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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  No.  135 


BORDEAUX  MIXTURE 


By  CHARLES  S.  CRANDALL 


URBANA,   ILLINOIS,   MAY,    1909 


SUMMARY  OF  BULLETIN  No.  135 

1.  Bordeaux  mixture  was  discovered  by  accident  in  the   fall   of   1882  by 
Professor  Millardet.  Page  205 

2.  Original  formulas  have  been  greatly  modified.    The  first  formula  con- 
tained more  than  six  times  the  copper  sulphate  and  nearly   12  times  the  lime 
per  gallon  of  water  that  is  used  in  the  present  standard  4-4-50  formula.    Page  207 

3.  It  is  conclusively  demonstrated  that  mixtures  made  with  air-slaked  lime 
are  not  only  extremely  injurious  to  foliage,  but  are  much  less  adhesive  than  are 
mixtures  made  with  fresh-slaked  lime.  Pages  210  and  288 

4.  The  chemical  reactions  that  occur  when  copper  sulphate  and  lime  are 
combined  take  place  in  a  manner  to  give  best  results  only  when  the  ingredients 
are    combined    ki    certain    definite    proportions.        Hence    formulas    should    be 
strictly  followed.  Page  212 

5.  Equal  and   full   dilution   of  the  milk  of  lime  and   the  copper   sulphate 
solution,  before  mixing,  gives  mixtures  that  are  least  injurious  and  of  maximum 
adhesiveness.  Page  213 

6.  With  all  precautions  taken  injuries  to  foliage  sometimes  occur  and  are 
not  to  be  avoided.     In  such  cases  injury  is  usually  associated  with  unfortunate 
weather  conditions.  Page  215 

7.  Rightly  made  Bordeaux  mixture  is   remarkably  adhesive.     When   once 
dried  on  the  leaves  it  is  not  easily  removed  by  rains,  but  continues  its  defensive 
action  for  long  periods.  Page  217 

8.  There  is  decided  advantage  in  the  maintenance  of  an  excess  of  lime  on 
the  leaves.     This  must  be  accomplished  by  subsequent  applications  of  milk  of 
lime  and  not  by  additions  of  lime  to  the  original  mixture.  Page  218 

9.  There  is  no  evidence  indicating  danger  to  orchard  trees  from  accumula- 
tion of  copper  sulphate  in  the  soil  as  a  result  of  spraying.  Page  219 

10.  Well  made  Bordeaux  mixture  contains  no  copper  in  solution,  but  small 
quantities  of  copper  become  soluble  very  soon  after  application  to  foliage.     The 
presence  of  free  calcium  hydroxide,  in  large  excess,  retards,  but  does  not  entire- 
ly prevent  solution  of  the  copper.  Page  225 

11.  Bordeaux  mixture  on  foliage  yields  soluble  copper  more  rapidly  under 
the  action  of  meteoric  waters  than  under  the  action  of  waters  artificially  applied. 
Injury  to  foliage  follows  the  action  of  rain   in  some  cases,  but  does   not  result 
from  water  artificially  applied.  Page  226 

12.  Physical  condition  of  leaves  at  time  of  spraying  is  important.     Leaves 
injured  by  insects,  or  attacked  by  fungi  are  especially  susceptible  to  additional 
injury  by  Bordeaux  mixture.  Page  233 

13.  Epidemics   of   the   trouble  known  as   "Yellowing  of   leaves"   appear  to 
have  no  relation  to  weather  conditions  and  no  evidence  has  been   found  that 
Bordeaux    mixtures    causes    yellowing.     Experiments    do    show    definitely    that 
copper  sulphate  solutions  cause  yellowing  and  that  the  degree  of  yellowing  de- 
pends upon  the  strength  of  the  solution.  Pages  234-237 

14.  Healthy  bark  of  trunk  and  branches  is  impervious  to  Bordeaux  mixture 
and  to  solutions  of  copper  sulphate.  Page  238 

15.  Copper  sulphate  solutions  varying  between  1:100  and   1:1000  when  ab- 
sorbed by   trees,   thru  wounds,    invariably  kill    the   leaves   which    then   become 
brown.  Page  238 

16.  In  one  instance  absorption  of  a  solution   1 :25000  was  followed  by  yel- 
lowing of  leaves.  Page  240 

17.  Examinations  of  drip  waters  from  sprayed  trees  show  the  early  appear- 
ance and  continued  presence  of  copper  in  solution.     They  also  show  the  extreme 
adhesiveness  of  Bordeaux  mixture  and  the  slow  solubility  of  the  copper. 

Pages  260-262 

18.  Conclusions.  Page  292 


BORDEAUX  MIXTURE 

BY  CHARLES  S.  CRANDALL,  Associate  Professor  of  Pomology 

INTRODUCTION 

Methods  of  warfare  against  fruit  pests — fungi,  bacterial  diseases 
and  insects — have  developed  in  a  wonderful  manner  during  the  last  few 
years.  The  devastations  of  parasites  have  forced  upon  fruit  growers 
the  conviction  that  strong  effort  in  the  direction  of  efficient  control  is 
the  only  salvation  for  the  fruit  business. 

The  idea  of  making  applications  to  fruit  trees  to  check  or  prevent 
the  ravages  of  insects  and  diseases  is  by  no  means  new.  Remedies  for 
fruit  tree  troubles  were  recommended  by  early  writers  and  it  seems 
probable  that  their  use  may  be  as  old  as  fruit  culture.  Early  remedies 
were  mainly  of  the  nature  of  repellents,  substances  which,  on  account 
of  bad  odors,  caustic,  or  other  disagreeable  properties,  were  thought 
capable  of  driving  away  insects  or  warding  off  disease.  In  a  few  cases, 
perhaps,  applications  were  made  before  invasion  and  with  the  definite 
purpose  of  preventing  attack,  but  more  frequently  applications  followed 
the  discovery  that  serious  injury  had  been  inflicted,  and  were  made  in 
an  endeavor  to  check  further  injury  by  driving  away  the  invaders. 
These  applications  were  made,  generally,  with  very  imperfect  knowl- 
edge of  the  organisms  responsible  for  the  injury  and  without  tangible 
basis  for  the  belief  that  the  nostrums  used  were  in  any  degree  effective 
against  the  particular  organisms  causing  the  injury.  It  follows,  that, 
while  there  were  frequent  reports  of  benefit,  the  major  portion  of 
efforts  expended  in  the  application  of  supposed  curative  substances 
failed  to  give  relief,  or  in  any  way  diminish  the  losses.  The  treat- 
ments here  referred  to  were  those  of  the  early  days  before  orcharding 
had  developed  as  a  distinct  business.  Fruit  plantations  were,  in  the 
main,  small,  mostly  home  farm  orchards.  Applications  were  intermit- 
tent, desultory,  without  much  system  and  never  on  an  extended  scale. 

Out  of  the  first  crude  efforts  have  grown  systems  of  procedure 
based  on  principles  that  have  been  worked  out  thru  detailed  investi- 
gations of  particular  parasites  and  thru  carefully  planned  and  skill- 
fully executed  experiments  with  remedial  applications. 

Those  investigators  who  have  specialized  on  the  problems  relating 
to  the  control  of  fruit  parasites  are  now  able  to  recommend  materials 
and  practices  from  the  basis  of  often  repeated  tests,  and  to  predict 
results  with  reasonable  confidence.  Always,  however,  with  the  express 
reservation  that  climatical  or  atmospheric  conditions  may  greatly  mod- 
ify or  entirely  reverse  the  results  obtained  under  normal  conditions. 
Altho  advancement  has  been  great,  it  can  not  yet  be  said  that  the 
business  of  combating  plant  parasites  has  reached  the  limits  of  develop- 
ment. Evolution  is  still  going  on.  Old  problems  are  modified,  new 
problems  appear,  and  new  materials  are  suggested  for  trial ;  so  that 
changes  in  procedure  are  constantly  occurring  and  the  practice  .of 

201 


202  BULLETIN  No.   135  [May 

spraying,  considered  in  its  entirety,  must  still  be  regarded  as  in  a  form- 
ative stage,  rather  than  as  bounded  by  definite  and  distinct  lines  of 
practice.  When  it  is  considered  that  little  more  than  two  decades  have 
passed  since  the  beginning  of  systematic  effort  to  control  the  parasites 
in  commercial  fruit  plantations,  it  is  evident  that  there  has  been  great 
progress  toward  the  mastery  of  these  problems.  It  is  also  apparent 
that  the  experiences  of  each  season  increase  the  general  understanding 
of  the  problems,  and  improve  the  effectiveness  of  remedial  applica- 
tions. 

The  present  state  of  efficiency,  it  should  be  understood,  has  not 
been  reached  over  a  perfectly  smooth  and  unobstructed  course.  There 
have  been  difficulties  to  overcome.  Records  of  experiments  with  ma- 
terials and  methods  do  not  show  an  unbroken  sequence  of  successes. 
There  have  been  failures,  results  have  been  negative,  mistakes  have 
been  made.  Trees  have  been  defoliated  and  fruit  has  been  ruined. 
These  things  have  served  as  retarding  agencies ;  but  considered  with 
the  aggregate  of  successful  operations  they  become  mere  incidents  such 
as  should  be  expected  to. attend  any  large  undertaking. 

The  chief  difficulty  attending  the  use  of  applications  for  control  of 
diseases  and  insects  has  been,  and  still  is,  that  the  compounds  applied 
too  frequently  exert  an  injurious  action  upon  foliage  and  fruit. 
Thru  the  whole  course  of  development  of  spraying  practices,  the 
absorbing  problem  for  both  pathologists  and  entomologists  has  been  the 
discovery  of  substances  which,  while  possessing  high  efficiency  as  fun- 
gicides and  insecticides,  are  at  the  same  time  harmless  to  foliage  and 
fruit.  Many  substances  known  to  possess  high  value  as  remedies 
against  particular  parasites  can  not  be  used  at  all  because  of  equally 
destructive  action  upon  the  host  plants.  Even  the  most  approved  of 
modern  remedies  are  not  uniformly  harmless.  In  careless  hands,  they 
very  frequently  inflict  serious  injury,  and  in  the  most  careful  hands, 
their  harmlessness  can  not  be  absolutely  depended  upon. 

Injury  to  foliage  and  fruit  by  materials  applied  as  spray,  has  often 
discouraged  beginners  and  called  forth  the  resolve  to  pursue  the  prac- 
tice no  further.  But  such  a  course  is  unwise.  Experience  has  taught 
that  control  of  parasites  is  essential  to  the  production  of  marketable 
fruit,  that  spraying  is  the  only  means  of  effecting  control,  and  that  in 
the  majority  of  cases  good  results  attend  the  practice.  The  remedy 
for  discouraging  results  lies  in  close  study  of  attending  circumstances, 
in  more  easeful  attention  to  the  details  of  preparation  and  application, 
in  short  in  discovery  of  the  difficulty  and  such  modification  of  practice 
as  will  prevent  its  future  occurrence. 

Investigation  of  spraying  compounds  in  their  relation  to  foliage  in- 
jury was  undertaken  by  the  Department  of  Horticulture  in  response  to 
a  popular  demand  for  information  on  the  subject.  It  was  commenced 
in  a  small  way  in  1905  and  has  been  in  progress  since.  The  work  is 
by  no  means  complete  and  this  bulletin  is  presented  as  a  report  of  pro- 
gress only,  and  not  as  a  finished  treatment  of  the  subject.  The  prob- 
lem is  complex,  presenting  many  distinct  phases.  On  the  physiological 
side  are  questions  bearing  upon  the  direct  effects  of  various  sprays 


1909]  BORDEAUX  MIXTURE  203 

upon  plant  cells  and  upon  the  development  of  those  changes  that  result 
in  the  injuries  observed ;  also  questions  involving  the  delicate  processes 
of  plant  assimilation  and  nutrition  and  the  relation  of  spray  compounds 
to  these  functions.  On  the  chemical  side  are  included  determinations 
of  the  composition  of  commercial  materials,  and  of  the  compounds 
formed  in  making  the  various  mixtures  used  in  spraying;  the  changes 
occurring  in  spray  mixtures  after  deposition  upon  the  plants,  and  the 
presence  of  foreign  substances  in  affected  tissues.  In  most  cases  the 
quantities  dealt  with  are  extremely  minute  and,  in  general,  the  chemical 
work  is  of  such  delicate  nature  as  to  call  for  a  high  degree  of  skill  and 
a  perfect  equipment. 

With  the  experience  of  each  season,  new  anomalies  are  presented 
out  of  which  grow  new  secondary  problems  that  add  to  the  difficulties 
of  the  major  problem.  One  of  these  problems  is  the  relation  of  spray- 
ing to  atmospheric  conditions  and  the  varying  phenomena  attendant 
thereon.  Experiences  here  are  varied  and  perplexing;  so  much  so  that 
several  seasons  will  be  necessary  to  fully  test  the  complications  arising 
thru  atmospheric  influences  and  to  correlate  them  in  such  manner 
as  would  warrant  definite  conclusions  that  could  serve  to  guide  practice. 

HISTORICAL 

The  list  of  really  important  substances  or  mixtures  used  as  insec- 
ticides and  fungicides  in  commercial  orchards  is  not  a  long  one  and 
some  brief  consideration  of  the  introduction  and  development  of  these 
remedies  may  not  be  out  of  place  here.  Arsenical  poisons  have  been 
the  chief  remedies  used  against  insects  and  of  these  Paris  green  came 
into  use  some  time  previous  to  1870  and  London  purple  was  introduced 
in  1871  or  1872.  Both  these  substances  were  used  as  remedies  for  the 
Colorado  potato  beetle  which  at  that  time,  was  destroying  the  potato 
crop  over  a  large  portion  of  the  country.  Strong  objections  were 
urged  against  the  use  of  these  poisons  because  of  supposed  danger  to 
human  life,  but  their  efficiency  as  insecticides  and  the  absence  of  fatali- 
ties following  continued  use  of  potatoes  as  food  soon  resulted  in  their 
general  acceptance  as  successful  remedies. 

The  prejudices  held  against  the  use  of  arsenical  poisons  on  pota- 
toes were  even  stronger  in  regard  to  proposed  applications  of  these 
substances  to  fruit  plants.  Extension  of  use  was  thus  considerably 
delayed,  but  as  early  as  1872  the  use  of  Paris  green  for  canker  worm 
on  apple  trees  was  reported  in  a  few  cases.  The  earliest  application 
of  Paris  green  as  a  remedy  for  codling  moth  appears  to  have  been  in 
1878  in  New  York,  but  altho  entire  success  was  reported  it  was 
some  years  before  applications  for  this  purpose  became  general.  In 
1881,  Professor  Cook  stated  before  the  Michigan  Horticultural  So- 
ciety (Report  1881,  p.  131)  that  he  had  used  Paris  green  successfully 
on  a  few  trees  of  his  own,  but  he  would  not  then  recommend  it  to 
others  because  of  the  dangerous  nature  of  the  substance.  By  the  year 
1886,  Paris  green  had  advanced  to  first  rank  as  an  orchard  insecticide 
and  its  use  on  a  large  scale  still  continues.  More  or  less  serious  injury 
to  foliage  commonly  attends  the  use  of  Paris  green,  and  has  been  pres- 


204  BULLETIN  No.  135  [May 

ent  since  its  first  introduction.  This  trouble  is  less  now  than  formerly, 
because  better  grades  of  Paris  green  are  obtainable,  and  because  of  the 
common  practice  of  combining  it  either  with  lime  alone  or  with  Bor- 
deaux mixture  containing  lime  in  excess.  Still,  it  sometimes  causes 
injury  notwithstanding  precautions  taken  to  render  it  safe.  London 
purple  has  always  been  destructive  to  foliage,  and,  for  this  reason,  is 
now  seldom  used  against  orchard  insects. 

Arsenate  of  lead  has  steadily  grown  in  favor  during  the  last  few 
years  and  is  now  quite  extensively  used.  (This  preparation  was  the 
outcome  of  an  effort  on  the  part  of  the  Gipsy  Moth  Commission  of 
Massachusetts  to  find  an  arsenical  poison  to  replace  Paris  green,  since 
Pairis  green  frequently  caused  serious  injury  to  foliage).  It  was  first 
used  in  1893.  Its  fine  division,  its  ability  to  remain  long  in  suspension 
in  water,  its  adhesiveness,  and  its  insolubilty  are  all  strong  points  in 
favor  of  this  compound,  and  were  it  not  for  its  somewhat  higher  cost 
it  would  soon  entirely  supersede  its  present  rival,  Paris  green. 

FUNGICIDES 

During  the  early  years  of  fruit  growing  in  this  country,  little 
trouble  was  experienced  from  parasitic  fungi,  but  as  years  passed  cer- 
tain diseases  became  troublesome.  The  fruit  most  seriously  affected 
was  the  grape.  During  the  years  preceding  1850,  grape  culture  as- 
sumed large  proportions,  and  considerable  areas,  in  regions  supposed  to 
be  especially  adapted  to  grapes,  were  given  up  to  this  crop.  Between 
1850  and  1860,  the  devastating  action  of  the  grape  diseases  known 
under  the  names  of  rot,  blight,  and  mildew  increased  year  by  year  and 
many  vineyards  that  were,  at  first,  profitable,  were  entirely  destroyed. 
The  threatened  ruin  of  the  grape  industry  turned  attention  to  remedies 
and  many  things  were  tried,  but  no  successful  means  of  combating  the 
trouble  was  discovered. 

In  1878  the  Downy  Mildew — Peronospora  viticola — a  native 
American  fungus  originally  parasitic  on  wild  grapes,  was  introduced 
into  France,  and  in  the  years  following  did  enormous  injury  to  the 
vineyards  of  the  more  important  wine  producing  districts.  The  Pow- 
dery Mildew — Uncinula  spiralis — had  long  been  a  pest  in  French  vine- 
yards, as  in  those  of  this  country,  and  had  for  years  been  successfully 
controlled  by  the  use  of  sulphur,  but  the  new  disease  because  of  its  en- 
tirely different  manner  of  growth  did  not  yield  to  the  sulphur  treat- 
ment, and  relief  was  sought  in  the  use  of  a  great  variety  of  substances. 
Finally  a  remedy  was  discovered,  the  introduction  of  which  marked 
the  beginning  of  a  new  era,  not  only  in  grape  culture,  but  in  the  cul- 
ture of  many  other  fruit  crops. 

DISCOVERY  OF  THE  FUNGICIDAL  ACTION  OF  COPPER 

The  discovery  that  compounds  of  copper  possessed  fungicidal 
properties  was  made  as  long  ago  as  1807.  In  that  year  it  was  proved 
that  copper  sulphate  in  dilute  solutions,  would  prevent  germination  of 
spores  of  wheat  smut — (Tilletia  tritici). 


1909]  BORDEAUX  MIXTURE  205 

Benedict  Prevost,  published  at  Montauban  in  1807  a  memoir,  on 
the  immediate  cause  of  smut  or  rust  in  wheat  and  gave  details  of  a 
series  of  experiments,  with  results  obtained.  On  page  60  is  the  follow- 
ing— "Thus  the  actual  sulphate  necessary  to  give  to  the  water  the 
power  of  preventing  the  rust  from  germinating,  at  a  low  temperature, 
does  not  exceed  1/400,000  of  its  weight,  and  1/1200,000  retards  its 
germination."1  This  discovery  does  not  appear  to  have  been  largely 
used  in  practice  and  there  is  no  suggestion  of  extending  its  application 
to  control  of  other  fungi.  During  the  following  50  years  there  is 
occasional  reference  to  treatment  of  seed  wheat  by  copper  sulphate 
solutions.  In  1861  W.  F.  Radclyffe,  reasoning  from  his  knowledge  of 
the  fact  that  "solution  of  vitriol  was  a  sure  remedy  for  smutty  wheat 
seed,  applied  with  a  watering  pot,  to  rose  bushes  affected  with  mildew 
a  solution  of  2  ounces  of  blue  vitriol  to  a  stable  bucket  of  cold  water. 
The  receipt  signally  succeeded,  and  the  Geants  are  perfectly  cleaned  of 
the  mildew."  '  Evidently  the  successful  treatment  here  reported  was 
not  repeated  as  no  later  mention  of  it  is  to  be  found.  No  further  ex- 
periments with  copper  compounds  are  reported  until  we  come  to  those 
of  Millardet. 

DISCOVERY  OF  BORDEAUX  MIXTURE 

What  was  first  known  as  the  "Copper  Mixture  of  Gironde"  and 
later  as  Bordeaux  mixture — the  "Bouillie  bordelaise"  of  the  French — 
was  discovered  by  accident  in  the  fall  of  1882  by  Professor  Millardet 
of  the  Faculty  of  Sciences,  Bordeaux,  France. 

The  following  is  the  account  of  the  discovery  as  given  by  Profes- 
sor Millardet:8 

"Since  the  appearance  of  mildew  in  France,  1878,  I  have  not 
ceased  to  study  Pcronospora  in  the  hope  of  discovering  a  weak  point  in 
its  development  that  would  permit  mastery  of  it.  The  results  of  my 
observations  are  to  be  found  recorded  in  various  publications.  I  had 
noticed,  in  the  course  of  my  researches,  that  the  summer  spores,  or 
conidia  of  the  Peronospora  readily  lost  their  power  of  germinating. 
This  observation  and  the  failure  of  all  the  treatments  that  had  been 
attempted,  resulted  in  the  formulation  of  this  conclusion — that  a  prac- 
tical treatment  of  mildew  ought  to  have  for  its  aim,  not  the  killing  of 
the  parasite  in  the  leaves  which  are  infected,  that  which  seems  impos- 
sible without  killing  the  leaves  themselves,  but  of  preventing  its  devel- 
opment by  covering  the  surface  of  the  leaves  with  various  substances 
capable  of  causing  the  spores  to  lose  their  vitality,  or  at  least  hindering 
their  germination." 

"Three  years  ago  I  was  searching  for  a  substance  which  would 
answer  the  purpose  that  I  had  outlined,  when  chance  placed  it  in  my 
hands.  The  last  of  October,  1882,  I  had  occasion  to  pass  thru  the 
vineyard  of  St.  Julian  in  Medoc.  I  was  not  a  little  surprised  to  see 
that  all  along  the  route  which  I  followed  the  vines  still  bore  leaves 
while  every  where  else  the  leaves  had  long  since  fallen.  There  had 

iComptes  Rendus  101   (1885)   p.   1225. 

2Gardener's  Chronicle  1861   p.  967. 

3Jour.  d'Agr.  Prat.  October  8,  1885,  pp.   513-514. 


206  BULLETIN  No.   135  [May 

been  some  mildew  this  year,  and  my  first  impulse  was  to  attribute  the 
persistence  of  the  leaves  along  the  road  to  some  treatment  which  had 
preserved  them  from  the  disease.  Examination  enabled  me,  indeed,  to 
ascertain  immediately  that  the  leaves  were  in  great  part  covered,  on 
the  upper  surface  with  a  slight  adherent  coating  of  a  bluish-white  pul- 
verulent substance." 

"Arriving  at  the  Chateau  Beaucaillon  I  questioned  the  manager, 
Mr.  Ernst  David,  who  fold  me  that  it  was  the  custom  in  Medoc  at  the 
turning  of  the  grape  to  cover  the  leaves  with  verdigris  or  sulphate  of 
copper  mixed  with  lime  in  order  to  keep  away  marauders ;  they,  seeing 
the  leaves  covered  with  coppery  spots,  were  not  bold  enough  to  taste 
the  fruits  hidden  beneath  for  fear  that  they  had  been  contaminated  with 
the  same  matter.  I  called  the  attention  of  Mr.  David  to  the  fact  of 
preservation  of  leaves,  which  question  was  discussed  and  I  made  him 
share  the  hope,  which  this  observation  raised  in  me,  of  finding  in  the 
salts  of  copper  the  basis  of  the  treatment  of  mildew.  Mr.  David  at 
first,  I  ought  to  say,  made  several  objections,  but  in  the  end  he  never- 
theless entered  completely  into  my  ideas  and  assisted  me  in  so  efficient 
a  manner  that  I  owe  to  him  the  best  part  of  the  final  success." 

The  year  following  (1883)  Professor  Millardet  made  numerous 
experiments  testing  various  compounds  against  the  mildew  and  all 
these  experiments  were  duplicated  by  Mr.  David  on  the  estate  at 
Medoc.  These  experiments  were  repeated  in  1884,  but  owing  to  the 
fact  that  the  mildew  did  not  develop  that  year,  gave  no  definite  results. 
The  results  in  1883  were  successful  in  demonstrating  the  efficiency  of 
the  Bordeaux  mixture  as  a  remedy  for  Peronospora  and  (after  publi- 
cation in  the  spring  of  1885  of  the  formulas  used),  the  Bordeaux  mix- 
ture was  applied  on  a  large  scale  by  several  proprietors  of  large  vine- 
yards. Wherever  the  mixture  was  used  the  mildew  was  held  in  com- 
plete control.  So  successful  were  the  results  that  the  remedy  at  once 
gained  general  favor  and  its  use  extended  rapidly. 

We  do  not  know  the  origin  of  the  use  of  the  copper  lime  mixture 
as  a  protection  against  trespassers,  but  the  custom  had  been  in  vogue 
for  some  years.  The  mixture  thus  used  was  of  the  consistency  of  thin 
mush  or  porridge  and  was  applied  to  the  vines  by  sprinkling  it  on  with 
a  small  broom.  The  first  mixtures  made  for  use  against  mildew  were 
based  upon  the  original  mixture  and  were  too  thick  to  allow  application 
by  spraying  with  a  pump  and  in  the  fine  state  of  division  which  later 
came  to  be  considered  desirable. 

During  the  year  1885,  and  in  the  following  years,  notably  1887, 
the  horticultural  and  viticultural  journals,  and  the  reports  of  societies, 
published  many  articles  on  the  general  subject  of  spraying,  on  the 
numerous  compounds  both  liquid  and  dust  form,  that  were  tried,  and 
particularly  on  Bordeaux  mixture,  which  seemed  everywhere  to  stand 
in  greatest  favor,  because  it  gave  the  best  results. 

There  was  some  controversy  over  the  priority  of  discovery  and 
several  claims  were  made  adverse  to  Millardet.  But  Professor  Millar- 
det in  an  article  on  the  history  of  copper  sulphate  as  a  remedy  for  mil- 
dew, appears  to  have  fully  established  his  claim  of  priority  of  discov- 


1909]  BORDEAUX  MIXTURE  207 

ery  and  of  interpretation  of  the  action  of  the  mixture.1-  No  further 
counter  claims  appeared  and  he  has  since  been  regarded  as  the  discov- 
erer and  introducer  of  Bordeaux  mixture. 

FIRST  FORMULAS 

Of  the  various  formulas  used  by  Professor  Millardet  in  his  exper- 
iments, the  one  that  gave  the  most  satisfactory  results  was  first  pub- 
lished2 by  him  in  the  spring  of  1885,  and  was  used  that  season  in  many 
vineyards  with  entire  success.  The  composition  is  as  follows : 

"In  100  litres  of  whatever  water  (well,  rain,  or  river) — dissolve  8 
kilos  of  commercial  sulphate  of  copper.  In  another  place  make  with 
30  litres  of  water  and  15  kilos  of  fat  stone  lime,  a  milk  of  lime  which  is 
mixed  with  the  solution  of  copper  sulphate." 

Converting  this  into  pounds  and  gallons  we  have : 

8  kilos  copper  sulphate 17.6366  pounds 

15  kilos   lime 33.0687  pounds 

130  litres  water 34.3421  gallons 

This  is  a  little  more  than  one  half  pound  of  copper  sulphate  to  the 
gallon,  and  almost  one  pound  to  the  gallon  of  lime ;  or  more  than  six 
times  the  copper  sulphate  and  nearly  twelve  times  the  lime  per  gallon 
of  water,  that  is  used  in  making  our  present  standard  mixture  on  the 
4-4-50  formula. 

At  an  early  stage  in  his  work  on  the  copper  compounds,  Millardet 
enlisted  the  services  of  his  .colleague,  Mr.  U.  Gayon,  a  chemist,  and 
they  worked  together  on  numerous  problems  that  developed  out  of  the 
experiments.  In  the  spring  of  1887  they  published  two  articles  jointly3 
in  which  a  considerable  reduction  in  the  proportion  of  copper  sulphate 
used,  is  recommended.  During  the  summer  of  1887,  field  experiments 
were  carried  on  in  three  large  vineyards  in  quite  widely  separated 
localities.  These  experiments  included  a  comparative  test  of  mixtures 
of  five  different  strengths,  ranging  from  the  mixture  used  the  previous 
year  consisting  of 

Copper  sulphate 6  kilos 

Lime 12  kilos 

Water s 100  litres 

(which  stafed  as  we  now  give  our  formulas  would  be  approximately  a 
24.9-49.9-50  formula)  clown  to  a  mixture  made  with 

Copper  sulphate 1  kilo 

Lime 340  grammes 

Water 100  litres 

(or  stated  in  our  terms,  a  4.1-1.4-50  formula).  In  this  last  the  lime 
used  is  the  minimum  amount  necessary  to  precipitate  all  the  copper 
sulphate,  and  the  authors  show  that  while  theoretically  this  is  a  safe 
and  effective  mixture,  practically  it  is  not  so,  because  of  the  great  likli- 
hood  of  using  impure  lime,  thus  leaving  in  solution  copper  which  would 
be  destructive  to  foliage. 


journal  d' Agriculture  Pratique,  December  3,   1885. 

2Annales  de  la  Societe  d' Agriculture  de  la  Gironde,   April   1,   1885. 

"Journal  d'Agriculture  Pratique.  May   19,  pp.   693-704;   May  26,  pp.   728-732,    (1887). 


208  BULLETIN  No.   135  [May 

In  the  experiments,  the  mixtures  containing  the  reduced  amounts 
of  copper  proved  equally  effective  with  the  strong  mixtures,  and  recom- 
mendations were  made  accordingly. 

Report  of  the  experiments  was  published  in  three  articles  in  the 
Journal  d' Agriculture  Pratique,  issues  of  May  3,  10,  17,  1888.  In  con- 
cluding this  report  the  authors  say — "So  then,  and  this  is  our  conclu- 
sion, of  all  the  liquids  proposed  for  the  treatment  of  mildew,  the  most 
active,  the  least  expensive  and  the  only  one  the  application  of  which 
may  be  absolutely  without  danger  for  the  vine,  is  the  Bordeaux  mixture 
composed  after  our  new  formulas."  (Page  693.) 

From  the  year  1887,  Bordeaux  mixture  was  widely  and  very  suc- 
cessfully used  in  the  wine  producing  districts  of  France  for  control  of 
the  grape  diseases.  Its  use  was  also  extended  to  potatoes  for  control 
of  potato  blight.  Beyond  these  two  crops,  however,  the  French  appear 
to  have  found  no  general  application  for  Bordeaux  mixture. 

INTRODUCTION  OF  BORDEAUX  MIXTURE  IN  THE 
UNITED  STATES 

Thru  the  Department  of  Agriculture  Bordeaux  mixture  was 
introduced  in  this  country  in  1887.  Agents  of  the  Department  con- 
ducted experiments  testing  various  compounds  for  control  of  grape 
diseases  and  a  number  of  individuals  tried  the  remedies  recommended 
by  the  Department.  Circular  No.  3  sent  out  by  the  Department  in 
May  1887,  gave  formulas  as  reported  in  French  Journals: 

Copper   sulphate 8  pounds 

Lime 10  pounds 

Water 20  gallons 

and 

Copper  sulphate 16  pounds 

•Lime 30  pounds 

Water 28  gallons 

Directions  for  making  mixtures  on  this  last  formula  end  with  this 
remark:  "Some  have  reduced  the  ingredients  to  2  pounds  of  sulphate 
of  copper  and  2  pounds  of  lime  to  22  gallons  of  water  and  have  ob- 
tained good  results".1  On  page  43  of  Bulletin  5  (1888)  this  remark  is 
made — "In  regard  to  Bordeaux  mixture,  it  has  been  found  that  when 
the  amount  of  sulphate  of  copper  contained  in  it  is  less  than  6-8  per- 
cent, its  efficacy  is  materially  diminished.  The  old  formula  (water 
22  gallons,  sulphate  of  copper  13  pounds,  lime  26  pounds)  is  the  one 
still  held  to  be  the  best.  The  'new  formula'  or  'mixture  for  general 
application'  consists  of : 

Water ". 22  gallons 

Sulphate   of    copper 6  pounds 

Lime ; 2  pounds 

Good  results  have  been  obtained  with  this  mixture,  but  it  is  advisable 
owing  to  the  often  impure  character  of  the  lime  obtainable,  to  increase 
the  proportion  of  this  substance." 


JU.   S.  Department  of  Agriculture  Bulletin   5,   1888,  p.   40. 


1909]  BORDEAUX  MIXTURE  209 


Galloway  in  his  report  for  the  year  1888  gives  the  formula: 

Copper  sulphate 6  pounds 

Lime 4  pounds 

Water 22  gallons 

During  the  seasons  immediately  following,  this  formula  was  used 
more  than  any  other.  But  as  the  possibilities  of  the  mixture  came  to 
be  better  understood,  and  its  application  was  extended  to  plants  other 
than  the  grape,  the  conviction  grew  that  reduction  in  strength  was  de- 
§irable,  and  in  many  cases  necessary  because  of  the  tender  nature  of 
the  foliage  to  be  treated.  Hence  a  great  variety  of  formulas  has  been 
reported.  Of  seventeen  stations  reporting  in  1891,  nine  used  the  6-4- 
22  formula;  two  used  6-4-25  formula;  two — Ohio  and  New  Jersey 
used  <\  4  50;  the  first  mention  I  find  of  this  formula.  The  other 
four  each  used  a  different  formula,  but  all  were  weaker  than  the  first 
given  above.  Of  seventeen  reporting  in  1894  only  one — Rhode  Island, 
used  the  6-4-22  formula,  while  nine  used  6-4-50;  three  used  4-4-50 
and  four  various  still  weaker  mixtures. 

By  1896  the  22  gallon  formula  had  disappeared  and  the  custom  of 
stating  formulas,  on  the  basis  of  water  content  fixed  at  50  gallons, 
came  into  use.  The  amount  of  copper  sulphate  has  varied  and  still 
varies  between  two  and  six  pounds  while  the  lime  remains  in  the  ma- 
jority of  cases  at  four  pounds.  The  Mississippi  Valley  and  regions 
west  accepted  the  4-4— 50  formula  as  a  standard  some  years  ago,  some- 
what earlier  than  did  most  eastern  fruit  sections.  Within  the  past  two 
or  three  years,  however,  there  has  developed  a  well  defined  movement 
towards  a  still  further  reduction  in  strength.  Right  practice  calls  for 
just  such  strength  as  will  do  the  work — control  scab  and  blotch  on  ap- 
ples ;  scab,  curl  and  brown  rot  on  peach ;  brown  rot  and  shot  hole  on 
plums,  and  so  on.  Material  applied  beyond  this  is  waste.  Success  has 
in  some  cases  attended  the  use  of  mixtures  very  weak  in  copper;  in 
other  cases  such  mixtures  have  failed  to  accomplish  the  purpose  of 
application.  In  still  other  cases  standard  mixtures  have  failed  to  give 
the  satisfactory  results  usually  expected.  It  is,  therefore,  not  surpris- 
ing that  men  of  experience  sometimes  doubt  their  own  judgment  and 
hesitate  in  making  choice  of  a  formula.  The  formula  is  one  factor, 
time  of  application  is  another,  and  prevailing  weather  conditions  at 
time  of  application  are  of  even  greater  importance.  If  it  were  possible 
to  forecast  correctly  weather  conditions  spraying  operations  could  be 
adjusted  to  insure  a  maximum  of  good  results,  but  weather  possibilities 
can  not  be  predetermined  with  certainty.  Hence  the  safe  thing  to  do 
is  to  provide  as  far  as  possible  for  contingencies  and  leave  the  matter 
of  formulas  to  be  adjusted  according  to  circumstances  that  seem  best 
at  the  immediate  time  of  application. 

The  immediate  success  of  Bordeaux  mixture  as  a  preventive  of  the 
ravages  of  parasitic  fungi  attacking  the  grape  led  to  a  wide  extension 
of  its  uses  and  its  universal  adoption  as  the  standard  remedy  for  the 
long  list  of  fungi  injurious  to  orchard,  garden,  and  field  crops.  In 


210  BULLETIN  No.   135  [May 

combination  with  either  Paris  green  or  arsenate  of  lead  it  is  used  in 
practically  all  of  the  orchards  and  small  fruit  plantations  in  the  state. 
It  is  therefore  an  important  factor  in  the  business  of  fruit  growing 
and  every  phase  of  its  relations  to  the  plants  treated  is  worthy  of  con- 
sideration. 

Serious  injury  to  foliage  and  fruit  sometimes  follows  the  applica- 
tion of  sprays  as  has  already  been  mentioned.  Why  do  these  injuries 
occur?  Why  do  no  injuries  occur  in  very  many  cases?  What  are 
the  conditions  attending  the  infliction  of  injury?  What  are  the  inciting 
causes?  Are  the  injuries  preventable?  These  are  some  of  the  ques- 
tions that  are  woven  into  an  investigation  of  Bordeaux  mixture  in  its 
relation  to  fruit  plants.  The  questions  are  simple,  yet  they  lead  among 
complex  chemical  reactions  and  obscure  functional  disturbances  that 

require  infinite  patience  in  observation  and  care  in  interpretation. 

-~s*  •'• 

MATERIALS  FOR  BORDEAUxlviixTURE 

Good  materials  are  necessary  to  make  a  safe  and  efficient  Bor- 
deaux mixture. 

COPPER  SULPHATE. — The  copper  sulphate  should  be  pure.  This 
ingredient  usually  contains  a  small  percentage  of  iron  sulphate,  but 
rarely  is  it  present  in  excess,  or  in  sufficient  quantity  to  interfere  with 
the  efficiency  of  the  copper  compound.  In  the  spraying  work  at  this 
Station  no  difficulty  has  been  experienced  in  securing  copper  sulphate 
of  satisfactory  purity. 

LIME. — There  is  often  difficulty  in  obtaining  lime  that  slakes  well 
and  effects  the  perfect  precipitation  of  the  copper.  All  commercial  limes 
contain  more  or  less  of  impurities.  If  the  percentage  of  calcium  oxide 
is  high,  the  lime  is  technically  known  as  "fat  lime" ;  this  oh  the  addi- 
tion of  water,  slakes  quickly  and  completely  and  will  perform  its  office 
in  the  compounding  of  Bordeaux  mixture  in  an  entirely  satisfactory 
manner.  If,  however,  the  lime  contains  a  large  percentage  of  mag- 
nesia, or  clay,  or  sand,  it  is  known  as  "poor."  Such  lime  slakes  slowly 
and  incompletely  and  does  not  make  a  satisfactory  Bordeaux.  Limes 
from  the  same  quarry  are  variable  and  for  this  reason  a  given  brand 
will  at  one  time  be  perfectly  satisfactory  and  at  another  time  unsatis- 
factory. This  uncertainty  regarding  the  purity  of  lime  makes  neces- 
sary the  use  of  a  greater  excess  than  would  be  necessary  if  pure  cal- 
cium oxide  could  be  obtained,  or  if  there  was  perfect  uniformity  in  the 
composition  of  commercial  lime. 

Under  no  circumstances  should  lime  that  is  at  all  air-slaked  be 
used.  Several  comparative  tests  between  mixtures  made  with  air- 
slaked  lime  and  those  made  with  fresh  water  slaked  lime  have  given 
positive  and  uniform  results,  demonstrating  conclusively  that  mixtures 
made  with  air-slaked  lime  are  not  only  extremely  injurious  to  foliage, 
but  are  much  less  adhesive  than  are  mixtures  made  with  the  fresh- 
slaked  lime. 

Several  brands  of  "hydrated"  or  "new  process"  lime  have  been 
placed  on  the  market.  Three  of  these  have  been  tested  in  the  making 


1909]  BORDEAUX  MIXTURE  211 

of  Bordeaux  mixtures  for  application  to  orchard  trees.  These  limes 
are  in  an  exceedingly  fine  state  of  division,  much  like  flour,  and  are 
readily  suspended  in  water.  The  precipitate,  in  Bordeaux  mixture  made 
with  "hydrated"  lime,  remains  in  suspension  equally  as  well  as  in  mix- 
tures made  with  fresh-slaked  lime.  In  this  respect  there  is  no  differ- 
ence in  the  limes.  However,  the  process  limes  are  not  so  satisfactory 
as  are  fresh-slaked  limes  for  two  reasons:  first,  the  Bordeaux  made 
with  them  is  somewhat  less  adhesive,  and  second,  in  a  comparative  test, 
side  by  side,  the  Bordeaux  made  with  process  lime  caused  more  injury 
to  leaves  than  did  the  ordinary  Bordeaux  made  with  fresh-slaked 
lime.  Doubling  the  quantity  of  hydrated  lime  does  not  materially  re- 
duce the  injury  to  foliage,  but  still  further  reduces  the  adhesiveness. 

As  the  experiences  of  each  season  are  correlated  and  studied  the 
conviction  grows  that  the  character  of  the  lime  is  an  important  factor 
in  the  compounding  of  a  proper  Bordeaux  mixture.  The  use  of  fat 
stone  lime  as  fresh  from  the  kiln  as  it  is  possible  to  get  it,  is  commend- 
ed, and  it  is  suggested  that  where  possible,  tests  be  made  of  the  slak- 
ing qualities  of  available  brands  and  the  results  allowed  to  govern  the 
decision  as  to  which  will  best  serve  the  purpose. 

WATER. — The  question  has  been  raised  whether  for  making  Bor- 
deaux mixture,  pond  water,  carrying  in  suspension  a  considerable 
amount  of  silt,  is  as  desirable  as  cistern  or  well  water.  Several  com- 
parative tests  have  been  made.  To  spray  large  commercial  orchards 
large  quantities  of  water  are  necessary  and  it  is  essential  that  the  sup- 
ply be  ample  and  conveniently  locatecl.  To  supply  the  demand,  excava- 
tions are  made,  in  the  orchard,  or  as  near  as  surface  contours  will  al- 
low, and  so  situated  that  surface  waters  can  be  conducted  into  them 
and  there  stored  for  use  at  the  time  for  spraying.  These  pond  waters 
are  always  considerably  discolored  by  the  abundant  sediment  held  in 
suspension.  In  comparative  tests  of  mixtures  made  with  pond  water, 
clear  cistern  water,  deep  well  water  and  distilled  water,  nothing  to  the 
disadvantage  of  the  pond  water  was  discovered.  The  pond  water  Bor- 
deaux has  a  dull  greenish  color  due  to  the  sediment.  In  settling  tests 
in  the  laboratory,  pond  water  Bordeaux  stands  between  that  made  with 
distilled  water,  which  settles  most  rapidly,  and  those  made  with  the  two 
other- waters  which  settle  at  practically  the  same  rate,  but  the  differences 
are  so  small  that  they  may  be  disregarded.  Pond  water  Bordeaux  is 
as  adhesive  as  are  the  others,  equal  in  efficiency,  and  considering  the 
advantage  of  convenience,  is  to  be  preferred  to  any  other  source  of 
supply. 

MAKING  BORDEAUX  MIXTURE 

No  less  important  than  the  character  of  the  ingredients  is  the 
manner  of  making  Bordeaux  mixture.  The  formulas  commonly  'rec- 
ommended have  grown  out  of  experiences  and  carefully  made  compa- 
rative tests  of  almost  all  possible  combinations.  They  can  be  depended 
upon  as  being  the  best  now  known  and  are  within  reach  of  everyone. 
Formulas  are  entitled  to  some  respect  because  they  represent  the 
thought  and  labor  of  experts.  The  man  of  experience  in  spraying  may 


212  BULLETIN  No.  135  [May 

find  it  desirable  to  modify  formulas  to  suit  special  conditions ;  this  he 
may  do  with  safety,  because  he  is  careful  to  maintain  proper  propor- 
tions and  exercise  the  usual  care  in  preparation.  For  the  beginner  it 
is  much  the  safer  plan  to  follow  the  formulas  as  given. 

Not  infrequently  the  man  of  little  experience  is  inclined  to  place 
higher  value  upon  his  own  judgment  than  upon  carefully  determined 
formulas  and  resorts  to  estimates  for  determining  quantities  of  ingred- 
ients to  be  used,  or,  attempts  to  follow  formulas  fail  through  careless- 
ness in  manipulation.  In  either  case,  grave  mistakes  are  likely  to 
occur.  Very  many  cases  of  serious  injury  to  orchard  foliage  have  been 
traced  directly  to  carelessness  or  inattention  to  the  details  of  determin- 
ing quantities  of  ingredients,  or  to  the  manner  of  combination  of  these 
ingredients.  It  is  also  a  mistake  to  do  the  work  in  what  chances  to  be 
the  most  convenient  method,  without  reference  to  correctness  of  the 
method. 

It  should  be  remembered  that  in  the  combination  of  lime  and  cop- 
'per  sulphate  chemical  reactions  occur  and  that  these  reactions  take 
place,  in  a  manner  to  give  best  results,  only  when  the  ingredients  are 
combined  in  certain  definite  proportions ;  hence  adherence  to  these  pro- 
portions, which  are  expressed  in  the  formulas,  cannot  be  too  strongly 
urged. 

For  the  proper  making  of  Bordeaux  mixture  certain  essentials  in 
the  way  of  barrels  or  tanks  and  necessary  tools  should  be  provided  be- 
forehand. The  kind  of  equipment  will  depend  upon  the  extent  of  the 
spraying  operations  in  prospect.  For  the  small  home  orchard,  requir- 
ing only  small  quantities  of  the  mixture  a  few  oil  barrels  as  containers 
and  a  small  slaking  box  will  serve  every  purpose ;  for  the  larger  com- 
mercial orchard,  where  spraying  is  done  from  one  or  more  two  hundred 
gallon  tanks,  every  device  that  will  diminish  the  labor  and  save  waste 
of  time  should  be  employed.  Here  the  elevated  platform,  so  located 
with  reference  to  pond  or  well  that  water  can  be  pumped  direct  to  the 
diluting  tubs  is  an  essential  feature.  This  platform  should  have  two 
parts,  one  higher  than  the  other;  on  the  lower  part  is  supported  a 
receiving  or  mixing  tank  of  somewhat  greater  capacity  than  the  spray 
tank,  at  such  distance  above  the  ground  as  will  allow  delivery  of  the 
mixture,  by  gravity,  to  the  top  of  the  spray  tank  driven  underneath. 
The  upper  platform  should  be  large  enough  to  accommodate  two  dilut- 
ing tubs,  four  or  more  barrels  for  stock  solutions,  and  a  slaking  box, 
and  still  leave  room  for  convenient  operation  of  the  pump.  It  should 
be  elevated  above  the  lower  platform  to  such  height  that  the  diluting 
tubs  can  be  adjusted  to  deliver  the  solutions  together  thru  a  strainer 
into  the  receiving  tank. 

The  equipment  provided,  we  may  now  give  attention  to  the  details 
of  mixing.  Stock  solutions  of  copper  sulphate  and  lime  should  be  pre- 
pared in  advance.  Fill  an  oil  barrel  with  50  gallons  of  water;  then 
suspend  in  the  water  a  coarse  sack  containing  50  pounds  of  copper  sul- 
phate. This  gives  a  solution  of  definite  strength — 1  pound  to  the  gal- 
lon. The  quantity  of  copper  sulphate  can  be  doubled  if  desired,  giving 
a  solution  of  2  pounds  to  the  gallon ;  however,  the  "pound  to  the  gal- 


1909]  BORDEAUX  MIXTURE  213 

Ion"  solution  is  the  one  most  frequently  used.  Solutions  thus  made 
will  keep  indefinitely,  if  protected  so  that  the  water  does  not  evaporate. 
The  amount  prepared  should  be  adjusted  to  the  extent  of  the  opera- 
tions. In  like  manner,  prepare  a  milk  of  lime  which  shall  contain  a 
definite  weight  of  lime  to  each  gallon  of  water.  Where  50  or  more 
pounds  of  lime  are  to  be  slaked  at  one  time,  the  shallow  box  is  to  be 
preferred  to  the  barrel,  because  it  affords  better  opportunity  to  control 
the  slaking.  The  success  of  the  mixture  depends  in  great  part  upon 
the  manner  in  which  the  lime  is  slaked.  The  two  common  faults  ob- 
served in  practice  are :  the  addition  of  too  little  water,  which  results  in 
the  development  of  too  much  heat  and  the  "burning"  of  the  lime.  In 
this  case  there  are  many  small  lumps  that  do  not  completely  slake  and 
will  be  thrown  out  when  the  lime  is  strained  into  the  tank.  The  second 
fault  is  the  addition  of  too  large  an  amount  of  water  resulting  in 
"drowning"  of  the  lime.  This,  likewise,  results  in  incomplete  slaking, 
and  therefore,  a  reduction  in  the  actual  amount  of  lime  added  to  the 
mixture.  In  some  cases  where  the  lime  is  neither  perfectly  fresh  nor 
of  great  purity  these  losses  may  so  reduce  the  amount  that  the  copper 
is  not  all  precipitated  and  serious  injury  follows.  Lime,  during  the 
process  of  slaking  should  have  constant  attention;  water  should  be 
added  in  small  amounts  as  needed  to  keep  the  action  even  and  to  in- 
sure that  perfect  slaking  which  can  be  obtained  in  no  other  way.  It  is 
best  to  slake  a  definite  number  of  pounds  and  when  thoroly  slaked 
transfer  to  a  barrel  containing  such  amount  of  water  as,  added  to  the 
quantity  used  in  slaking  will  give  a  milk  containing  a  definite  quantity 
of  lime  to  the  gallon.  Having  the  stock  solutions  prepared,  the  next 
step  is  dilution  preparatory  to  mixing. 

The  diluting  tubs  should  each  have  capacity,  in  excess  of  one  hun- 
dred gallons.  A  palm  oil  cask  of  250  gallons  capacity,  cut  in  half,  will 
supply  two  tubs  that  serve  the  purpose  admirably.  We  will  suppose 
that  the  standard  4-4-50  formula  is  to  be  used  and  that  the  mixture  is 
to  be  made  in  lots  of  200  gallons.  In  one  diluting  tub,  place  16  gallons 
of  the  stock  solution  of  copper  sulphate,  made  up  1  pound  to  the  gal- 
lon, then  add  84  gallons  of  water.  The  first  lot  should  be  carefully 
measured  and  the  height  at  which  it  stands  in  the  tub  marked,  so  that 
in  filling  for  succeeding  mixtures,  it  is  only  necessary  to  fill  to  the 
mark.  Thoroly  agitate  the  milk  of  lime  and,  if  it  has  been  made 
up  1  pound  to  the  gallon,  transfer  16  gallons  to  the  other  tub  and  fill 
up  with  water  in  like  amount  as  for  the  copper  sulphate  solution.  We 
now  have  100  gallons  of  copper  sulphate  solution  and  an  equal  quantity 
of  milk  of  lime.  This  is  on  the  plan  of  full  dilution  before  mixing, 
which  has  been  shown  by  experience  to  possess  advantages  over  other 
ways  of  mixing,  such  as  adding  a  concentrated  solution  of  copper  to 
fully  diluted  lime,  or  concentrated  lime  to  fully  diluted  copper  sul- 
phate, or  combining  the  two  ingredients  in  concentrated  form  and  then 
diluting.  By  this  method  of  equal  and  full  dilution  before  mixing,  the 
chemical  action  between  the  copper  sulphate  and  lime  appears  to  take 
place  quicker  and  more  completely,  than  by  the  other  methods.  The 
resulting  mixture  settles  less  rapidly,  is  less  frequently  injurious,  and 


214  BULLETIN  No.   135  [May 

attains  a  maximum  of  adhesiveness.  These  points  of  difference  have 
been  determined  by  field  and  laboratory  experiments  with  mixtures 
made  in  the  different  ways,  and  we  have  no  hesitation  in  urging  equal 
and  full  dilution  before  mixing  as  being  the  best  plan  to  follow.  In 
mixing,  equal  streams  may  be  conducted  directly  into  a  strainer  sup- 
ported over  the  receiving  tank,  or  the  streams  may  meet  in  a  short 
trough  which  terminates  on  the  strainer.  Before  starting  the  streams, 
the  milk  of  lime  must  be  thoroly  stirred  and  this  agitation  should 
continue  until  the  mixing  is  completed  in  order  to  insure  uniformity 
in  the  combination. 

There  are  a  number  of  small  details  in  connection  with  a  mixing 
outfit  such  as  has  been  described,  that  may  be  modified  in  various 
ways,  and  cheapened  or  made  more  expensive,  according  to  the  wishes 
of  the  individual,  but,  while  cheapness  is  desirable  the  better  appliances 
are  likely  to  be  the  cheaper  in  the  end.  Any  device  that  will  economize 
time,  by  expediting  the  filling  of  tanks,  or  that  will  reduce  the  liability 
to  accidents  which  result  in  loss  of  material  is  worthy  of  consideration, 
and  a  few  dollars  expended  in  this  direction  are  well  invested. 

It  is  an  unpleasant  fact  that  much  spraying  is  done  badly;  this 
means  that  much  money  is  thrown  away.  Such  waste  is  believed  to  be 
avoidable  because  it  has  its  origin  in  carelessness  and  inattention  to 
details. 

The  common  sources  of  trouble  in  spraying  as  determined  by  ob- 
servation and  investigation  of  many  specific  cases  may  be  summarized 
under  three  heads : 

,  1.  Use  of  impure  or  improper  materials,  as,  for  example  an 
adulterated  brand  of  Paris  green  which  contains  an  undesirable  amount 
of  free  soluble  arsenic,  or  of  air-slaked  lime  in  making  Bordeaux  mix- 
ture. There  is  no  excuse  for  the  use  of  air-slaked  lime,  and  trouble 
with  Paris  green  can  be  avoided  by  purchasing  a  brand  of  approved 
merit. 

2.  Carelessness  in  making  the  compounds.     Guessing  at  weights 
and  measures  and  mixing  in  the  easiest  rather  than  in  what  has  been 
demonstrated  to  be  the  right  way.     These  are  easily  avoidable  sources 
of  trouble  for  which  there  is  no  excuse. 

3.  Improper  and  ineffective  application.  Much  material  is  wasted 
and  possible  benefits  are  lost  thru  poor  work  in  application.     Right 
application  depends  upon  the  man  who  handles  the  pole,  and,  if  this 
man  is  inattentive,  lazy,  and  in  too  great  haste  to  finish,  an,  at  best,  un- 
pleasant task,  there  is  certain  to  be  uneven  distribution ;  parts  of  trees 
within  easy  reach  sprayed  in  excess  and  more  remote  parts  untouched. 
It  is  difficult  to  eliminate  this  source  of  trouble,  because  it  depends 
upon  the  character  of  the  help  obtainable,  and  often  this  is  inefficient 
and  unreliable.     The  nearest  approach  to  a  remedy  is  reached  in  as 
close  and  constant  supervision  as  it  is  possible  to  give. 

Of  these  three  sources  of  error,  the  first  two  can  be  entirely  elim- 
inated and  the  third  greatly  mitigated,  by  that  reasonable  care  that  is 
commonly  given  to  other  branches  of  the  orchard  business.  For  the 
attainment  of  best  results,  it  is  necessary  to  keep  clearly  in  mind  the 


1909]  BORDEAUX  MIXTURE  215 

purpose  for  which  the  spraying  is  done,  and  to  respect  the  smallest  de- 
tails that  promote  good  work  and  count  for  efficiency. 

But  even  when  all  known  precautions  have  been  taken  and  every- 
thing possible  done  to  promote  success,  difficulties  are  sometimes  en- 
countered. Leaves  are  burned,  fruit  is  russeted,  and  epidemics  of 
chlorotic  foliage  occur  that  affect  the  performance  of  the  trees.  These 
troubles  are  very  frequently  complained  of,  and,  while  in  many  cases 
these  injuries  result  directly  from  errors  in  practice,  there  have  been  a 
sufficient  number  of  cases  of  injury  following  spraying  by  experienced 
and  careful  men  to  show  that  injuries  are  not  always  preventable. 

THE  CHEMISTRY  OF  BORDEAUX  MIXTURE 

The  chemistry  of  Bordeaux  mixture,  the  reactions  that  take  place 
when  copper  sulphate  solution  and  milk  of  lime  are  mixed  together, 
and  the  exact  nature  of  the  compounds  formed  appears,  even  at  this 
date,  to  be  involved  in  some  obscurity. 

Considerable  work  on  the  chemical  side  has  been  done,  but,  so  far 
as  I  have  been  able  to  ascertain,  no  complete  investigation  has  been 
reported,  such  as  would  clear  up  all  the  perplexing  phenomena  that  have 
been  observed  in  connection  with  the  mixture.  Millardet  and  Gayon,1  with- 
out going  into  the  chemical  details,  state  that  the  copper,  as  deposited 
on  the  leaves,  is  in  the  form  of  copper  hydrate  (Cu  (OH)2).  Accord- 
ing to  these  authors,  the  copper  hydrate  deposited  remains  insoluble 
until  all  the  calcium  hydrate  has  been  neutralized  by  the  carbon  dioxide 
of  the  air.  The  time  required  for  this  depends  upon  the  excess  of 
lime  used  in  compounding  the  mixture.  Five  mixtures  were  made 
with  varying  amounts  of  lime,  the  precipitate  dried,  pulverized,  and 
definite  quantities  spread  on  filter  paper.  These  papers  were  so  ar- 
ranged that  when  rain  or  spray  was  passed  thru  them  it  could  be 
caught  and  examined  for  copper.  The  mixture  containing  least  lime 
yielded  soluble  copper  in  four  days  and  as  the  lime  increased  the 
time  elapsing  before  the  appearance  of  copper  lengthened  to  twelve 
days.  These  experiments  indicate  that,  in  well  made  Bordeaux,  no 
copper  is  left  in  solution. 

Chester2  gives  the  reactions  in  making  Bordeaux  mixture  as  fol- 
lows :  "In  the  addition  of  the  milk  of  lime  to  a  solution  of  copper  sul- 
phate, the  lime  in  solution  precipitates  the  copper  as  cupric  hydroxide 
forming  at  the  same  time  a  slightly  soluble  sulphate  of  lime.  These 
two  salts,  together  with  an  excess  of  lime  remain  in  supension  in 
Bordeaux  mixture.  The  reaction  is  simple. 

CuSO4,  5H20+CaO,H2O=Cu(OH)2+CaSO4+5H2O". 

In  the  same  year,  Professor  Livio  Sostegni,  in  an  article  on  the 
chemical  composition  of  Bordeaux  mixture,3  reaches  the  following  con- 
clusions : 

1.  "In  the  so  called  Bordeaux  mixtures  prepared  with  ordinary 
quick  lime  there  almost  always  remain  in  solution  small  quantities  of 

iMillardet  and  Gayon.     Jour.    d'Agr.   Prat.   May   17,    1887,   p.    701. 

2F.  D.  Chester.     Jour.  Mycol.  6  (1890)  p.  21. 

3L.    Sostegni,   L.   Stazioni  Sperimentali   Agarie  Italiane  Vol.    19,  p.    139.     August,    1890. 


216  BULLETIN  No.   135  [May 

copper,  which  in  some  cases  remain  undetected  by  any  common  reac- 
tion, but  which  are  easily  recognized  and  determined  by  the  electrolytic 
method.  The  quantity  of  lime  used  has  an  influence;  in  fact  when  a 
large  excess  is  used  only  very  small  traces  of  copper  can  be  detected." 

2.  "The  quantity  of  copper  which  may  remain  in  solution  is  con- 
siderably greater  when  slaked  lime  is  used,  or  lime  which  has  been 
slightly  carbonated.     Also  when  the  lime  is  added  directly  to  the  so- 
lution of  copper  sulphate.     If  incompletely  slaked  lime  is  used,  or  even 
lime  not  well  diluted,  the  quantity  of  copper  which  may  remain  in  so- 
lution is  sometimes  considerable,  altho  the  liquid  may  be  decidedly 
alkaline.     The  maximum  of  copper  salt  in  solution  is  found  when  caus- 
tic lime  in  the  form  of  powder  is  added  directly  to  the  sulphate  solution 
a  little  at  a  time." 

3.  "The  copper  is  precipitated  in  the  Bordeaux  mixture  in  the 
form  of  the  hydrate,  basic  sulphate,  and  the  double  basic  sulphate  of 
copper  and  calcium.    It  seems  that  in  this  last  form,  which  is,  however, 
richest  in  sulphate  of  lime,  the  small  quantities  of  copper  which  are 
found  are  held  in  solution." 

The  conclusions  reached  by  Dr.  Sostegni  would  be  more  acceptable 
had  they  been  reached  by  using  milk  of  lime,  as  used  in  making  Bor- 
deaux mixture,  instead  of  lime  water.  This  use  of  lime  water  raises 
the  question — would  milk  of  lime  give  the  same  result?  Fairchild' 
comments  on  this  point  and  adds  "the  fact  that  no  mention  is  made 
of  the  changes  in  color  of  the  mixture  corresponding  with  similar 
changes  taking  place  when  one  of  the  alkalis  proper  is  added  to  the 
copper  sulphate,  also  leads  to  the  belief  that  he  has  overestimated  the 
proportion  of  the  basic  salt  present  in  the  mixture  as  ordinarily  pre- 
pared." 

The  direct  statement,  that  the  copper,  deposited  on  the  leaves  in 
spraying,  is  in  the  form  of  copper  hydrate,  has  been  so  frequently  re- 
peated that  it  has  quite  generally  come  to  be  accepted  as  a  piece  of  com- 
mon knowledge.  Occasionally,  mention  is  made  of  the  possible  pres- 
ence of  basic  sulphates,  but  most  writers,  even  tho  recognizing  in 
their  own  minds  the  obscurity  of  the  reactions,  prefer  the  simple  ac- 
cepted statement  rather  than  attempt  proof  by  argument  or  investiga- 
tion. 

The  latest  contribution  to  the  chemistry  of  Bordeaux  mixture  that 
has  come  to  my  notice  is  that  by  Professor  Umfreville  Pickering2,  Di- 
rector of  the  Woburn  Experiment  Station,  England,  which  appeared 
in  December  1907,  and  from  which  I  wish  to  make  a  brief  quotation. 
"It  is  remarkable  that  the  nature  of  the  substance  constituting  this 
mixture  has  not  yet  been  elucidated.  The  reaction  occurring  is  gen- 
erally represented  as  resulting  in  the  formation  of  copper  hydroxide 
altho  occasionally  it  is  suggested  that  a  basic  sulphate  may  be  formed 
and  an  equation  is  given  representing  a  basic  sulphate  (2CuO, 
SO3)  which,  so  far  as  is  known  has  no  existence.  That  copper  hy- 
droxide is  the  product  of  the  reaction  scarcely  admits  of  serious  con- 


iFairchild,  D.  G.,  U.   S.  Dept.  Agr.   Div.   Veg.  Path.   Bui.  6   (1894),  p.   14. 

'Pickering,  Prof.   U.,  Jour.  Chem.   Soc.  London,  Vols.  XCI  and  XCH,  1907,  pp.  1988  and  2001. 


1909]  BORDEAUX  MIXTURE  217 

sideration,  for  this  hydroxide  as  is  well  known,  loses  its  water  and  its 
blue  color  in  a  very  short  time,  turning  black,  whereas  Bordeaux  mix- 
ture remains  quite  blue  for  an  indefinite  period."  "In  Bordeaux  mix- 
ture made  with  milk  of  lime,  there  must  be  free  lime,  and  generally, 
calcium  carbonate,  mechanically  mixed  with  the  precipitate,  and  any 
direct  investigation  of  the  composition  of  this  precipitate  would  be  of 
little  value.  Lime  water,  therefore,  was  used  instead  of  milk  of  lime; 
but  even  then  any  analysis  of  the  precipitate  was  practically  impossible, 
for  it  is  very  bulky  and  difficult  to  wash  whilst  water  as  will  be  shown, 
partly  decomposes  it,  as  does  carbon  dioxide." 

In  summarizing  Professor  Pickering  says — "The  substances 
formed  on  the  addition  of  lime  to  copper  sulphate  as  in  the  preparation 
of  Bordeaux  mixture  are  dependent  upon  the  proportions  of  lime  used 
and  may  be  either : 

1.  4CuO,  SO3,  0.06  CaSO4 

2.  5CuO,  SO3,  0.25  CaSO4 

3.  lOCuO,  SO3,  1.30  CaSO4 

4.  lOCuO,  SO3,  4CaO,  SO3 

and  probably  5.     lOCuO,  SO3,  lOCaO,  SO3 

or  6.     CuO,  3CaO 

that  present  in  most  cases  probably  4." 

Here  again  are  analyses  made  with  lime  water  instead  of  milk  of 
lime,  and  if,  as  Professor  Pickering  says,  analyses  of  the  precipitate 
even  where  lime  water  is  used  is  "practically  impossible"  it  seems  likely 
that  the  exact  changes  that  occur  in  making  Bordeaux  mixture  are 
doomed  to  remain  in  some  degree  mysterious,  at  least  for  the  layman. 

ADHESIVENESS 

Rightly  made  Bordeaux  mixture  is  remarkably  adhesive.  When 
once  deposited  on  foliage,  it  does  not  readily  yield  to  the  washing 
action  of  rains,  but  remains  and  continues  its  defensive  action  for  long 
periods.  The  addition  of  soap  to  Bordeaux  mixture  increases  its  ad- 
hesiveness. This  was  first  shown  by  Galloway1  in  1893  in  experiments 
devised  to  test  the  effect  of  the  addition  of  various  substances  upon 
the  spreading  of  the  mixture  on  leaves  of  cereals.  It  was  further 
demonstrated  by  Guillon  and  Gouirand2  in  experiments  conducted  for 
the  express  purpose  of  testing  the  relative  adhesiveness  of  mixtures 
variously  modified.  They  used  two  sets  of  mixtures,  one  freshly 
made,  the  other  24  hours  after  preparation.  Both  sets  were  tested  on 
glass  plates  and  also  on  grape  leaves.  The  authors  conclude  that  ad- 
hesiveness decreases  with  age,  particularly  in  the  case  of  Bordeaux 
mixtures  made  with  soda,  or  to  which  soap  has  been  added.  They 
also  conclude  that  "the  compounds  are  on  the  whole  more  adhesive, 
the  nearer  they  are  to  being  neutral."  In  the  same  year  (1898),  Joseph 
Perraud3  reported  a  test  of  adhesiveness  for  21  combinations  of  vari- 
ous substances,  including  Bordeaux  mixtures  made  in  different  ways. 

1B.  T.  Galloway.    Experiments  in  the  Treatment  of  Rusts  Affecting  Wheat  and  Other  Cereals. 

Jour.   Mycol.   VII    (1893),   p.    202. 
2Compt.    Rend.   127   (1898),   pp.   254,  256,  423-424. 
aPerraud,   Joseph.     Jour.   d'Agr.   Prat.    1898,   pp.   814-816. 


218  BULLETIN  No.  135  [May 

He  concludes  that  the  adhesiveness  of  copper  mixtures  is  much  less 
upon  the  fruit  than  upon  the  leaves  of  the  grape ;  also  that  adhesive- 
ness is  relatively  weak  for  old  mixtures.  The  mixtures  ranking  highest 
in  adhesiveness  in  his  experiments  appear  in  the  following  order. 

1.  Bordeaux  with  carbonate  of  soda — slightly  alkaline. 

2.  Bordeaux  with  fat  lime — -slightly  alkaline. 

3.  Bordeaux  with  equal  parts  of  copper  sulphate  and  fat  lime. 
A  more  recent  and  elaborate  test  of  adhesiveness  is  that  made  by 

W.  Kelhofer1  and  reported  in  1907.  It  was  found  that  under  the  in- 
fluence of  artificial  rain,  or  of  short  natural  showers,  the  Bordeaux 
mixture  made  with  carbonate  of  soda  possessed  greater  adhesiveness 
than  did  Bordeaux  made  with  lime;  but,  under  a  long  continued  gentle 
rain  Bordeaux,  made  with  lime,  took  first  rank  in  adhesiveness.  The 
author  ascribed  the  difference  to  the  action  of  certain  constituents  of 
the  atmosphere  and  of  rain  water,  particularly  ammonium  nitrate  and 
carbon  dioxide.  These  constituents,  acting  singly,  or  together,  exert 
a  stronger  solvent  action  upon  the  soda  Bordeaux  than  upon  the  lime 
Bordeaux.  By  experiments,  it  was  determined  that,  as  between  the 
two  constituents  named,  the  carbon  dioxide  exerted  much  the  greater 
action,  and  also  that  alkaline  Bordeaux  was  much  more  adhesive  than 
neutral  or  nearly  neutral  mixtures.  Kelhofer's  final  conclusion  is  "that 
Bordeaux  mixture  with  a  moderate  excess  of  lime,  say  about  1  kg  to 
2  kg  of  copper  sulphate  can  be  recommended  under  all  conditions." 

It  is  now  quite  generally  accepted  that  the  benefits  that  accrue 
from  the  addition  of  soap  and  other  substances  are  not  sufficient  to 
warrant  their  use  in  compounding  mixtures  for  use  in  commercial 
orchards.  Bordeaux  mixture  without  additions  when  well  made,  is,  at 
once,  the  most  adhesive  and  the  most  efficient  of  all  substances  that 
have  been  used  on  any  extended  scale  as  preventives  against  the  attacks 
of  parasitic  fungi. 

Adhesiveness  depends  very  much  upon  the  making  of  the  mixture, 
and  attention  to  this  cannot  be  too  strongly  urged.  Variation  in  the 
proportions  of  copper  sulphate  and  lime,  beyond  certain  well  defined 
limits,  decreases  adhesiveness.  Insufficient  lime,  or  lime  of  poor 
quality,  or  lime  that  is  in  any  degree  air-slaked  will  not  give  a  maxi- 
mum of  adhesiveness.  Neither  will  too  great  an  excess  of  the  best 
quality  of  lime.  The  proportions  giving  greatest  adhesiveness  are 
fairly  well  indicated  in  the  formulas  accepted  for  general  use.  Those 
mixtures  are  best  in  adhesiveness,  and  in  efficiency,  in  which  an  ap- 
proximation of  equal  parts  of  copper  sulphate  and  lime  are  maintained. 
This  has  been  demonstrated  over  and  over  again  in  the  experiments 
conducted  by  this  station.  That  there  is  decided  advantage  in  the 
maintenance  of  an  excess  of  lime  upon  the  foliage  is  also  clearly  shown 
by  our  experiments,  but  this  excess  must  be  provided  by  subsequent 
applications  and  not  by  increasing  the  proportion  in  the  original  mix- 
ture. When  Bordeaux  has  once  dried  down  upon  the  leaves,  further 
additions  of  lime  do  not  affect  its  adhesive  qualities,  but,  if  lime  is 


JKelhofer,  W.    Zeitschrift  fur  Pflanzenkrankheiten   17   (1907),  pp.   1-12. 


1909]  BORDEAUX  MIXTURE  219 

used  in  greatly  increased  quantity  in  making  the  mixture,  it  has  a  de- 
cided influence  in  diminishng  adhesiveness. 

ACCUMULATION  OF  COPPER  IN  THE  SOIL 

Bordeaux  mixture  applied  to  trees  in  spraying  eventually  finds  its 
way  into  the  soil  and  the  fear  has  been  expressed  that  the  accumulation 
of  copper  in  the  soil  will  in  time  result  in  injury  to  the  trees.  This 
possibility  was  suggested  some  years  ago  by  owners  of  vineyards  in 
France  and  several  investigators  instituted  experiments  bearing  upon 
the  question. 

Millardet  and  Gayon  cite1  the  fact  that  M.  Garros,  proprietor  of 
a  large  vineyard  deposited  annually  for  ten  years,  large  quantities  of 
copper  sulphate  about  the  bases  of  his  grape  vines  in  an  attempt  to 
control  Phylloxera.  The  amount  was  between  5  and  10  grams  per 
vine  per  year  which  would  represent  from  44.6  pounds  to  89.2  pounds 
per  acre  per  year.  The  vines  showed  no  effects,  but  continued  to  grow 
and  fruit  in  a  normal  way. 

Girard2  reported  to  the  French  Aqademy  in  1895  the  results  of  a 
series  of  experiments  extending  over  three  years.  He  estimated  the 
amount  of  copper  deposited  in  the  vineyard  in  one  season  at  13.38 
pounds  per  acre ;  he  assumes  that  in  100  years  the  quantity  would  be 
100  times  as  great  or  1338  pounds  per  acre.  This  amount  he  added, 
at  one  time,  to  a  plat  on  which  was  grown  wheat,  oats,  clover  and 
beets.  The  planting  extended  over  an  adjoining  plat  of  equal  area, 
prepared  in  the  same  way,  but  not  treated  with  copper.  Comparison 
of  the  crops  harvested  from  the  two  plats  serves  as  a  basis  for  his 
conclusion,  which  is  expressed  as  follows :  "The  agricultural  results 
that  I  have  just  made  known  being  added  to  those  that  other  experi- 
menters have  already  published,  demonstrate  in  a  certain  manner  that 
the  repetition  during  a  very  long  time,  during  a  century,  of  the  treat- 
ment of  the  grape  or  potato,  by  copper  mixtures,  has  no  influence  either 
from  the  point  of  view  of  the  abundance  of  the  harvests,  or  in  respect 
to  their  quality." 

That  large  amounts  of  copper  sulphate  in  the  soil  act  injuriously 
upon  plants  has  been  shown  by  Beach3  who  grew  peas,  tomatoes  and 
wheat  in  prepared  soils  containing  2  percent  and  5  percent  by  weight  of 
copper  sulphate.  Germination  was  less  rapid  in  the  prepared  soils,  than 
in  the  check  soils,  altho  the  number  of  seeds  germinated  was  greater 
in  the  prepared  soils.  Plants  on  the  prepared  soils  were  of  a  darker 
green  color  than  were  the  control  plants,  but  they  were  much  dwarfed, 
matured  earlier  and  yielded  less.  The  roots  of  the  plants  on  the  pre- 
pared soil  made  very  little  growth  as  compared  with  the  plants  on 
normal  soils.  In  these  experiments  the  amount  of  copper  sulphate 
added  to  the  soil  is  excessive ;  far  beyond  any  possible  accumulation 
that  could  result  from  spraying  as  practiced  in  commercial  orchards. 

The  possible  amount  of  copper  sulphate  that  may  reach  the  soil 
in  the  commercial  spraying  of  one  season  is  from  1/1200  to  1/1500  the 

your.   d'Agr.   Prat.   May   19,   1887,  p.   704. 

2Girard,  Aime.     Compt.   Rend.   120   (1895),  p.   1147-1152. 

SS.   A.   Beach.     N.   Y.    Sta.    Bui'.   41.     1892. 


220  BULLETIN  No.  135  [May 

amount  in  the  soil  containing  2  percent  as  used  in  the  experiments 
referred  to  above.  Orchards  that  have  been  sprayed  for  a  number  of 
years  have  shown  no  deterioration  that  can  be  ascribed  to  the  presence 
of  copper  in  the  soil.  It  has  been  suggested  that  accumulations  of 
copper  in  the  soil  are  responsible  for  the  epidemics  of  yellow  leaves, 
but  there  are,  as  yet,  no  definite  observations  or  experiments  that  serve 
to  support  this  suggestion. 

INJURIES  TO  FOLIAGE 

The  injuries  which  have  been  under  consideration  at  this  station 
are :  First — the  burning  or  "brown  spotting"  of  parts  of  leaves.  Second 
— the  yellowing  and  falling  of  leaves. 

Just  what  relation  these  two  injuries  have  to  each  other  cannot 
be  definitely  stated.  In  certain  cases,  yellowing  appeared  to  supple- 
ment browning.  Badly  brown  spotted  leaves  became  yellow  and  fell. 
In  one  case,  of  1000  yellow  leaves  gathered  under  a  tree,  that  had  been 
sprayed  with  a  solution  of  copper  sulphate,  each  leaf  had  several  to 
many  brown  spots,  or  else  had  some  portion  of  the  margin  browned. 

On  the  other  hand,  leaves,  free  from  brown  spots,  may  become 
yellow  and  fall.  Yellowing  is  commonly  epidemic  in  character  and 
•may  occur  on  the  same  trees  three  or  four  times,  during  a  season. 
Brown  spotted  leaves  may  turn  yellow  and  fall,  or  may  persist,  and 
the  uninjured  portions  may  continue  to  perform  their  functions  until 
the  end  of  the  season.  The  beginning  of  yellowing  appears  to  prompt 
the  completion  of  the  absciss,  or  separative  layer,  at  the  base  of  the 
petiole,  and,  within  48  hours,  the  leaves  are  ready  to  drop  at  the  slight- 
est touch.  A  shower  of  rain,  during  an  advanced  epidemic  of  yellow- 
ing, will  greatly  change  the  appearance  of  affected  trees,  by  the  re- 
moval of  all  yellow  leaves.  Yellowing  is  more  serious  than  brown 
spotting  because  affected  leaves  are  entirely  destroyed.  It  is  also  more 
erratic  in  appearance  and  duration,  and  presents  more  anomalies  in 
development.  The  causes,  too,  are  more  obscure  and  more  difficult 
to  prove. 

BURNING  OR  "BROWN  SPOTTING"  OF  LEAVES 

The  leaf  injuries  most  frequently  observed  and  most  often  the 
cause  of  complaint  from  orchard  owners,  are  brown  spots,  within 
whose  limits  the  tissue  is  dead.  These  spots  appear  on  a  portion  of 
the  leaves,  or,  in  bad  cases,  on  practically  all  leaves.  They  are  usually 
sharply  delimited,  and  may  be  irregular  or  often  circular  in  form. 
Sometimes  the  part  affected  may  be  the  tip  of  the  leaf,  or  it  may  be 
a  narrow  line  along  the  margin.  The  dead  areas  or  spots  may  be 
few  or  numerous,  large  or  small.  They  may  or  may  not  increase  in 
size,  after  first  appearance.  If  little  or  no  increase  in  size  occurs,  sur- 
rounding parts  may  remain  green  and  the  leaves  continue  to  perform 
their  functions,  altho  their  capacity  is  diminished,  in  proportion  to 
the  amount  of  tissue  affected.  In  some  cases  the  brown  spots  on 
many  leaves  increase  until  the  leaves  die.  In  other  cases,  while  not 
entirely  killed,  leaves  are  so  badly  affected,  and  perform  so  small  a 


1909]  BORDEAUX  MIXTURE  221 

part  of  their  normal  functions,  that  growth  is  checked  and  preparation 
of  buds  for  the  following  year  is  nearly  suspended. 

Trees  need  their  full  complement  of  foliage  in  order  to  make 
proper  growth,  ripen  the  wood,  and  prepare  for  the  crop  to  follow ; 
hence  the  loss  of  any  portion  of  the  working  leaf  surface  is  detrimental 
and  such  loss  should  be  prevented  if  possible.  While  spray  mixtures 
often  cause  such  brown  spotting  as  is  described  above,  it  must  not  be 
assumed  that  all  brown  spotting  is  the  result  of  spraying.  Other 
causes  produce  similar  injuries  and  it  is  a  common  mistake  to  ascribe 
to  spraying,  injuries  for  which  spraying  is  in  no  way  responsible.  Late 
spring  frosts  and  high  winds,  accompanying  cold  storms,  are  some- 
times accountable  for  the  browning  of  foliage,  as  was  the  case  in 
many  orchards  in  the  spring  of  1907,  and  again  in  1908.  The  injury 
noted  was  of  uneven  distribution,  being  most  pronounced  where  ex- 
posure was  greatest  and  gradually  decreasing  until  it  disappeared  in 
the  more  protected  portions  of  the  orchards.  Leaf  tips  and  margins 
were  most  affected  but  often  there  were  irregular  browned  areas,  dis- 
connected from  the  marginal  injury.  Certain  fungi,  as  for  example 
Spheropsis  malorum,  often  mark  the  leaves  of  apple  trees  with  brown 
spots,  that  in  the  early  stages  may  be  mistaken  for  the  injury  from 
spraying.  The  color  of  the  spots  is  the  same,  but  there  is  a  certain 
regularity  in  form  that  does  not  belong  to  injuries  inflicted  by 
spraying,  and  this  regularity  forms  a  ready  means  of  distinction. 
Moreover,  as  the  spots  become  older  they  assume  an  ash  gray  color 
that  easily  distinguishes  them  from  spots  resulting  from  spray.  A 
considerable  number  of  orchards,  in  Marion,  Clay,  and  Richland  coun- 
ties, exhibit  this  form  of  brown  spotting  from  fungi.  Leaf  eating  in- 
sects often  eat  holes  in  leaves  or  consume  marginal  strips,  and,  as  the 
exposed  edges  turn  brown,  the  injuries  are  mistaken  for  spray  injuries. 

The  occurrence  of  brown  spots  on  foliage  that  has  been  sprayed 
varies  greatly  with  individual  trees.  Vigorous,  healthy  trees  are  often 
free  from  injury,  while  the  weaker,  less  vigorous,  are  as  often  serious- 
ly injured.  There  is,  too,  a  difference  in  susceptibility  to  injury  and 
this  difference  varies  with  the  seasons.  In  some  years,  owing  usually 
to  unfavorable  weather,  foliage  comes  out  in  a  condition  of  general 
debility  and  is  easily  injured  by  agencies  that,  in  other  seasons,  would 
be  harmless.  Again,  there  may  be  an  early  and  abundant  infliction  of 
apple  scab  and  aftef  it  there  is  great  certainty  of  serious  brown  spot- 
ting from  spraying. 

One  other  cause  contributory  to  brown  spotting  by  spray  is  de- 
serving of  mention  and  that  is  what  may  be  termed  the  minor  insect 
injuries.  These  injuries  are  inflicted  by  a  great  variety  of  insects,  and 
they  are  of  such  a  nature  as  to  escape  casual  observation ;  yet,  in  the 
aggregate,  they  are  serious,  because  they  render  the  leaves  liable  to 
greater  injuries  by  spraying.  Numerous  field  trials  have  shown  that 
brown  spots  result  after  the  direct  application  of  spray  compounds  to 
broken  places  in  the  leaf  cuticle.  The  same  compounds,  namely,  Bor- 
deaux mixtures,  solutions  of  copper  sulphate,  white  arsenic,  and  Paris 
green  suspended  in  water,  are  found  to  exert  the  poisonous  in- 


222  BULLETIN  No.  135  [May 

fluence  very  slowly,  and  very  often  not  at  all,  on  leaves  having  un- 
broken cuticle.  These  experiments,  taken  in  connection  with  the  fre- 
quent injury  observed,  lead  to  the  opinion  that  fruit  tree  leaves  are 
often  not  nearly  so  free  from  these  minor  injuries  as  is  likely  to  be 
inferred  from  casual  examination. 

These  injuries  are  naturally  most  abundant  in  uncultivated  or- 
chards and  in  those  where  lack  of  care  allows  undisturbed  harbor  and 
breeding  ground  for  all  kinds  of  insects.  As  illustrating  the  preva- 
lence of  these  small  injuries,  it  may  be  stated  that  critical  examination 
of  6000  leaves,  taken  at  random  from  60  different  trees,  gave  only  27, 
or  less  than  ]/2  percent  of  absolutely  perfect  leaves,  altho  the  gen- 
eral appearance  of  the  foliage  on  these  trees  was  good.  This  last  phase 
of  leaf  injury  needs  further  study  than  has  yet  been  given  it,  but  the 
facts  thus  far  gathered  emphasize  the  necessity  of  controlling  early 
attacks  of  apple  scab  and  indicate  that  minor  leaf  injuries  should  re- 
ceive more  attention. 

SPRAYING  AS  A  CAUSE  OF  BROWNING  OR  BURNING 

Having  mentioned  the  various  causes  other  than  spraying  that 
directly  or  indirectly  produce  the  brown  spotting  or  burning  of  foliage, 
we  may  now  return  to  spraying  as  a  cause.  Injuries,  directly  caused 
by  spraying,  do  occur,  and  have  occurred,  ever  since  copper  compounds 
and  arsenites  were  first  applied  to  plants.  Millardet  frequently  re- 
ferred to  injuries  to  foliage,  and  all  writers,  who  treat  of  spraying, 
have  more  or  less  to  say  on  the  subject.  The  ideal  spray  compound 
that  will  be  perfectly  effective  against  orchard  pests,  and,  at  the  same 
time,  perfectly  harmless  to  foliage,  on  all  occasions  and  under  all  con- 
ditions, has  not  yet  been  discovered.  Of  all  the  various  preparations 
used,  Bordeaux  mixture  most  nearly  approximates  the  ideal,  but  its 
harmlessness  cannot  be  absolutely  depended  upon.  Many  experiments 
have  been  conducted  in  the  endeavor  to  find  means  for  insuring  harm- 
less action,  but  up  to  the  present  time  results  have  not  been  univer- 
sally successful.  Differences  of  opinion  have  arisen  among  experi- 
menters regarding  the  exact  manner  in  which  injuries  occur,  and  even 
regarding  the  particular  ingredients  of  the  mixture  that  cause  the 
injury.  Some  have  held  that  injury  should  be  ascribed  to  the  caustic 
action  of  the  lime,  particularly  in  cases  where  applications  have  been 
made  to  young  foliage.  Most  investigators,  however,  now  agree  that 
brown  spotting,  resulting  from  Bordeaux  mixture,  is  caused  solely  by 
the  copper  contained  therein ;  but  opinions  are  still  widely  different 
as  to  the  exact  manner  in  which  the  injuries  are  inflicted.  It  is  essen- 
tial that  the  causes  of  the  injuries  be  understood  before  preventive 
measures  can  be  intelligently  investigated. 

The  question  is  an  exceedingly  delicate  one,  and,  altho  answers 
have  been  attempted  by  several  trained  investigators,  there  is  still  reas- 
able  doubt  as  to  the  exact  manner  in  which  injuries  are  caused.  There 
appear  to  be  two  important  phenomena  involved,  which,  while  linked 
together,  the  one  preceding  and  essential  to  the  other,  are  yet  separate 
and  distinct.  These  phenomena  are,  the  solution  of  the  copper  and  the 


1909]  BORDEAUX  MIXTURE  223 

transmission  of  the  toxic  influence  to  the  cell  protoplasm.  The  two 
problems  are  then — 

First:  Under  what  conditions,  and,  thru  what  agencies,  does 
the  copper,  deposited  on  leaves  in  Bordeaux  mixture,  become  soluble? 
and — 

Second :  How  does  this  soluble  copper  establish  connection  with 
the  protoplasm  of  the  leaf  cells,  and  exert  its  poisonous  influence 
thereon  ? 

SOLUTION  OF  THE  COPPER  IN  BORDEAUX  MIXTURE 

It  has  already  been  stated,  that,  at  the  time  of  application,  Bor- 
deaux mixture  contains  no  soluble  copper.  As  spread  upon  the  leaves, 
the.  copper  is  insoluble,  or  at  least  very  slowly  soluble.  If  the  copper 
were  absolutely  insoluble,  its  fungicidal  power  would  be  inoperative. 
The  mere  presence  of  the  metal,  while  it  may  be  able  to  inhibit  germi- 
nation of  spores  in  immediate  contact  with  solid  particles,  would  not 
give  the  observed  protective  effect  over  large  leaf  surfaces.  There 
must  be  moisture,  carrying  a  certain  percentage  of  copper  in  solution, 
to  accomplish  ,the  defensive  action  desired.  The  agencies,  thru 
which  the .  copper  deposited  on  the  leaves  becomes  soluble,  and  the 
rapidity  with  which  solution  takes  place,  are  matters  that  have  received 
attention  at  the  hands  of  several  investigators.  The  carbon  dioxide 
of  the  atmosphere  is  frequently  referred  to  in  the  literature  of  Bor- 
deaux mixture  as  a  chief  factor  in  rendering  copper  soluble.  Often 
the  statements  appear  to  imply  that  it  is  the  only  agency  in  operation. 
There  is  'very  good  testimony,  supported  by  direct  observation  and  ex- 
periment, to  prove  that%  carbon  dioxide  does  have  solvent  action  on 
copper  hydroxide,  but  it  is  believed  there  are  other  agencies,  that, 
operating  alone,  or  in  conjunction  with  carbon  dioxide,  are  equally 
effective.  The  amount  of  carbon  dioxide  contained  in  meteoric  waters 
is  extremely  minute,  and,  in  cases  where  relatively  large  amounts  of 
copper  are  found  in  solution,  in  waters,  collected  from  sprayed  trees, 
it  is  thought  that  the  solvent  action  of  carbon  dioxide  may  have  been 
supplemented  by  the  action  of  other  agencies.  Possibly  these  agencies 
are  the  ammonium  compounds,  nitrates  and  nitrites,  or  some  other  con- 
stituent of  the  waters  or  the  atmosphere ;  or  the  influence  may  rest 
in  some  agency  entirely  independent  of  the  possibilities  here  suggested. 
Results,  obtained  from  some  of  the  experiments  made,  have  suggested 
some  interesting  studies  concerning  the  points  involved.  These  studies, 
it  is  hoped,  can  be  made  during  the  present  year.  Millardet  and  Gayon 
draw  conclusions  regarding  the  effectiveness  of  carbon  dioxide  as  a 
solvent  for  copper  hydroxide  and  in  these  conclusions  make  several 
references  to  its  action.  In  summing  up  the  results  of  one  series  of  ex- 
periments they  conclude  that1  "in  the  first  place  it  happens  that 
water  from  rain  and  dew  in  consequence  of  its  carbonic  acid  and  car- 
bonate of  ammonia  dissolves  a  sufficient  amount  of  copper  hydroxide 
which  is  on  the  surface  of  the  leaves,  either  to  completely  prevent  the 
germination  of  conidia  of  peronospora  in  this  water,  or  at  least  it 
cannot  take  place  in  a  normal  manner." 

^our.  d'Agr.   Prat.   February  23,   1887,  p.    161. 


224  BULLETIN  No.   135  [May 

These  authors  held  it  proved  by  their  experiments  that  excess  of 
lime  in  Bordeaux  mixture  entirely  prevents  solution  of  the  copper  as 
long  as  calcium  oxide  remains  on  the  leaves.  "We  have  proved  that 
the  copper  hydroxide  contained  in  a  drop  of  mixture  is  only  soluble  in 
rain  and  dew  when  the  lime  which,  in  the  actual  mixture  is  found  in 
enormous  excess,  is  completely  neutralized,  especially  by  the  carbon 
dioxide  of  the  atmosphere.  As  long  as  a  drop  of  mixture  moistened 
with  water  shows  a  perfect  alkaline  reaction,  that  is  to  say,  so  much 
so  that  pure  lime  is  found  in  solution,  the  copper  hydroxide  remains 
in  it  in  an  insoluble  state  in  the  meteoric  waters.1 " 

This  statement  by  Millardet  and  Gayon  is  based  upon  an  experi- 
ment which  was  repeated  several  times  with  uniform  results.  This  ex- 
periment was  as  follows  :2  "April  10  we  prepared  the  following  five 
types  of  mixture. 

No.  1       No.  2       No.  3       No.  4       No.  5 

Copper  sulphate,  grams 16.00        15.00        15.00        15.00        15.00 

Lime,  grams 3.36          3.36      .   6.72        13.44        26.88 

Distilled  water,  litre 1  1111 

As  may  be  seen  number  1  contains  1  gram  of  copper  sulphate  in  excess. 
Number  2  contains  exactly  the  quantity  of  lime  necessary  to  precipitate 
the  copper  sulphate ;  analysis  showed  that  there  was  neither  an  excess 
of  copper  nor  of  lime.  Number  3  contains  twice  as  much  lime  as  num- 
ber 2.  Number  4  contains  twice  as  much  as  number  3.  Finally 
Number  5  whose  composition  corresponds  to  that  of  the  ordinary  mix- 
ture contains  twice  as  much  as  number  4.  These  five  mixtures  were, 
at  once  dried  in  an  oven  at  36  degrees  C. ;  then  the  products  of  the 
dessication  were  finely  pulverized  in  a  mortar.  Ten  grams  of  each 
of  these  dried  mixtures  was  spread  in  a  thin  layer  of  about  two  milli- 
meters thickness  between  Berzelius  papers  supported  below  by  a  silk 
gauze,  and  tied,  at  the  same  time  as  this  latter,  on  five  glass  dialyzing 
dishes  of  equal  opening.  The  necessary  precautions  had  been  taken  to 
determine  if  the  paper  and  the  gauze  of  the  apparatus  were  capable  of 
absorbing  noteworthy  quantities  of  copper." 

"April  12th  in  the  evening,  these  five  dishes  were  exposed  in  the 
garden  in  an  open  place.  From  the  13th,  they  were  watered  simul- 
taneously by  all  the  rains  which  fell.  When  rain  did  not  fall  each  dish 
received  equal  quantities  of  rain  water  collected  beforehand.  The  ves- 
sels were  placed  separately  on  glass  funnels  which  drained  into  test 
tubes  into  which  water  poured  on  the  dializers  was  collected.  Every 
two  or  three  days  the  waters  collected  from  each  of  the  five  dishes  was 
removed  at  the  same  time,  and  analyzed  separately.  The  successive 
order  of  appearance  of  the  copper  in  the  waters  which  had  passed 
thru  the  mixtures  was  as  follows : 

Mixture  No.  1,  April  17 
Mixture  No.  2,  April  19 
Mixture  No.  3.  April  24 
Mixture  No.  4,  April  25 
Mixture  No.  5,  April  30 


ijour.   d'Agr.   Prat.    May  19,    1887,   p.    700. 

*Millardet  and  Gayon.     Jour.   d'Agr.    Prat.   May    19,    1887,   pp.    701-702. 


1909]  BORDEAUX  MIXTURE  225 

Other  experiments  t>f  the  same  nature  made  by  'watering  with 
rain  water  leaves  of  spindle  tree  and  of  boxwood,  previously  sprayed 
with  these  same  five  types  of  mixture,  gave  similar  results.  In  general, 
the  less  lime  contained  in  the  mixture  the  more  quickly  did  copper  ap- 
pear in  the  water  passed  over  the  leaves." 

According  to  these  experiments,  there  is  no  soluble  copper  present 
until  complete  neutralization  of  the  lime  is  accomplished.  The  time  of 
first  appearance  of  copper  in  solution,  in  the  waters  collected,  depends 
upon  the  amount  of  lime  in  the  mixture,  and  varies  from  5  to  18  days. 
It  must  follow  that  fungicidal  action  of  the  copper  is  delayed  corre- 
spondingly, because,  only  copper  in  solution  is  effective  in  preventing 
germination  of  spores.  Laboratory  experiments  at  this  station,  which 
are  given  in  detail  on  other  pages,  gave  results  that  accord  with  those 
obtained  by  Millardet  and  Gayon  in  the  experiments  given  above.  In 
these  experiments  Bordeaux  in  crystallizing  dishes,  both  dry  and  in- 
termittently wet,  gave  no  soluble  copper  at  the  end  of  65  days,  and 
sprayed  trees,  also  dry  and  frequently  moistened,  gave  no  soluble  cop- 
per to  water  with  which  the  leaves  were  washed  at  the  end  of  54  days. 
The  experiments  of  Millardet  and  Gayon  would  have  been  more  satis- 
factory had  more  explicit  information  been  given  regarding  the  waters 
that  passed  thru  the  mixtures.  We  are  told  that  "From  the  13th 
they  were  watered  simultaneously  by  all  the  rains  that  fell.  When 
rain  did  not  fall,  each  dish  received  equal  quantities  of  rain  water  col- 
lected beforehand."  Experiments  at  this  station  indicate  a  remarkable 
difference  in  action  between  direct  meteoric  waters,  and  water  arti- 
ficially applied ;  and  it  is  to  be  regretted  that  advice  is  not  given  regard- 
ing the  amount  and  character  of  the  natural  rains,  and  also  of  the 
waters  applied  artificially  in  the  experiments  quoted. 

Statements  to  the  effect  that  fungicidal  action  of  Bordeaux  nr'x- 
ture  is  delayed,  are  based  upon  the  supposed  insolubility  of  copper  hy- 
droxide in  the  presence  of  free  calcium  hydroxide.  It  is  believed,  how- 
ever, that  Bordeaux  mixture  is  effective  from  the  moment  of  applica- 
tion.- In  repeated  experiments,  in  which  spores  of  Fusicladium,  in 
water,  were  spread  on  leaves  of  apple  trees,  infection  was  entirely  pre- 
vented on  leaves  to  which  Bordeaux  was  applied  some  hours  later ; 
while  infection  was  abundant  on  untreated  leaves. 

All  our  field  experiments  bearing  upon  the  solution  of  copper  hy- 
droxide have  given  results  opposed  to  those  obtained  by  Millardet  and 
Gayon  and  to  the  results  of  our  own  laboratory  experiments.  They 
show  quite  conclusively,  that  while  there  is  no  soluble  copper  present 
at  the  time  of  application,  it  is,  in  some  way,  brought  into  solution  in 
small  quantities,  very  soon  after  application;  and,  further,  that  copper 
hydroxide  continues  to  become  soluble,  even  while  calcium  oxide  is 
still  present  in  excess.  As  a  specific  example  our  tree  number  1907 
A  may  be  cited.  Here  the  third  drenching  application  of  Bordeaux  was 
completed  at  11 :30  a.  m.  June  21.  Rain  amounting  to  0.1  inch  fell  28 
hours  later.  The  water  collected  carried  14.9  milligrams  of  copper 
in  solution  per  litre.  Copper  was  found  in  measurable  quantities  in  all 
subsequent  waters,  but  the  waters  did  not  become  neutral  until  late  in 
the  season. 


226  BULLETIN  No.   135  [May 

Comparison  of  sprayed  trees  exposed  to  rain  and  dew  with  trees 
similarly  sprayed,  protected  from  rain  and  dew,  and  sprayed  with  cis- 
tern water  show,  by  the  larger  amounts  of  copper  in  solution,  that 
meteoric  waters  possess  solvent  powers  that  do  not  belong  to  the  water 
artificially  applied.  It  is  also  clearly  indicated  by  injuries  inflicted 
under  meteoric  waters,  and  absence  of  injury  under  artificially  applied 
waters,  that  the  mere  presence  of  moisture  is  not  the  only  essential  to 
injury,  but  that  meteoric  waters  carry  some  influence  that  belongs  to 
them  alone,  or  to  them  in  connection  with  some  other  atmospheric  con- 
dition. The  tests  with  carbonated  waters  indicate  an  influence  of  car- 
bon dioxide,  favorable  to  the  solution  of  copper,  but  do  not  point  to  it 
as  responsible  for  any  increase  in  injury  to  foliage. 

From  those  experiments  in  which  sprayed  trees  were  continu- 
ously supplied  with  a  large  excess  of  lime,  it  appeared  that  injury  to 
foliage  was,  in  part,  prevented,  altho  copper,  in  solution,  continued 
to  appear  in  the  strongly  alkaline  water  collected. 

The  suggestion  is  made  by  several  authors  that  the  leaves  of 
sprayed  plants  may  exude  some  organic  substance  having  solvent  ac- 
tion upon  copper  hydroxide,  but  the  writer  has  been  unable  to  find 
proof  that  this  occurs  with  apple  leaves ;  and  efforts  to  ascertain  the 
truth  thru  experiments  have  been  thus  far  attended  with  negative 
results  only.  Swingle1  suggests  that  "It  is  possible  that  the  drops  of 
rain  or  dew  standing  for  some  time  on  the  leaves  or  other  parts  of 
plants  may  absorb  from  superficial  cells  sugar  or  other  substances  that 
may  serve  to  increase  the  solubility  of  the  copper."  Clark2  makes  this 
definite  assertion — "the  host  plant,  too,  is  active  in  dissolving  the 
Cu(OH)2".  He  made  an  experiment  in  which  matter  from  leaves  of  a 
peach  tree  sprayed  with  Bordeaux  and  having  the  leaves  moistened 
several  times  on  the  previous  day,  gave  a  copper  reaction ;  and  further, 
leafy  twigs  from  the  sprayed  tree  soaked  some  hours  in  distilled  water 
gave  up  copper  to  the  water  as  was  determined  by  a  test  which  gave  a 
marked  reaction. 

This  author  further  says  "the  epidermis  of  leaves,  altho  pro- 
tected by  a  cuticle,  is  well  known  to  be  more  or  less  permeable  to  the 
dissolved  substances  occurring  in  the  cell  sap,  particularly  along  the 
union  of  the  epidermal  cells.  When  the  dew  is  on  the  leaf  we  have 
two  solutions — the  dew  drop  without  and  the  cell  sap  within — sepa- 
rated by  a  more  or  less  permeable  membrane.  The  result  of  these  con- 
ditions must  result  in  the  exosmosis  of  at  least  some  of  the  contents  of 
the  cell  sap,  which,  coming  in  contact  with  the  copper  hydroxide  ad- 
hering to  the  leaf  surface  causes  more  or  less  of  it  to  pass  into  solu- 
tion." 

Bain8  refers  to  the  varnish  like  covering  of  young  peach  leaves,  to 
the  secretion  of  glands  terminating  marginal  dentations,  which,  when 
dried,  closely  resembles  gum  arabic,  and  also  to  secretions  from  petiolar 
glands,  but  as  the  result  of  experiments,  concludes  "that  neither  of 

Swingle.     Bui.  9.     Div.  Veg.   Phys.   and  Path.,  U.   S.   Dept.   Agr.,    1896,  p.    20. 

2Bot.    Gaz.    33    (1902),   p.    42. 

3S.   M.   Bain,  Tenn.   Sta.   Bui.   Vol.   15,  No.   2.     April,   1902,  pp.   53-54. 


1909]  BORDEAUX  MIXTURE  227 

these  secretions  can  play  any  important  part  in  producing  the  injury  of 
copper  hydrate  to  the  leaves."  From  the  fact  that  injury,  following 
application  of  pure  basic  copper,  was  confined  almost  exclusively  to 
marginal  teeth,  he  raises  the  question  "whether  this  greater  marginal 
injury  is  due  to  the  greater  permeability  of  the  cuticle  over  the  glands 
or  to  the  mere  presence  of  the  secretion  there."  From  other  facts 
brought  out  in  his  investigation  this  author  regards  it  as  more  probable 
"that  this  increased  marginal  injury  is  due  simply  to  the  greater  per- 
meability of  the  cuticle  over  the  glandular  surface  of  the  teeth." 

Schander1  holds  the  view  that  the 'copper  on  the  leaves  does  not 
come  into  solution  in  any  appreciable  quantity  except  under  direct  ac- 
tion of  germinating  spores.  He  says  "Upon  the  basis  of  my  experi- 
ence I  do  not  believe  that  enough  soluble  copper  compounds  form  upon 
the  leaf  to  kill  the  spores  of  fungi,  but  I  assume  with  Clark  that  on  the 
whole,  fungi  dissolve  enough  copper  from  the  precipitate  of  Bordeaux 
mixture  adhering  to  the  leaf  to  kill  them."  This  author  also  thinks 
that,  in  some  cases,  injury  arises  from  copper  that  has  been  brought 
into  solution  thru  certain  atmospheric  conditions.  He  distinguishes 
three  groups  of  poisonous  effects  of  Bordeaux  mixture ;  first,  the  plant 
secretes  an  acid ;  this  has  solvent  action  on  copper  hydroxide,  which,  as 
brought  into  solution  is  taken  up  by  the  leaves  and  injury  follows.  This 
is  thought  to  be  the  case  in  Fuschia  and  CEnothera.  Second,  the 
secretion  is  alkaline,  but  acts  as  a  solvent  for  copper  in  the  case  of  the 
bean  (Phaseolus  multiflorus).  The  secretion  in  this  case  takes  place 
from  the  glandular  bases  of  the  leaf  hairs  and  it  is  from  these  glandu- 
lar bases  that  injury  starts.  Bean  leaves  are  especially  susceptible  to 
injury  by  copper  salts.  Schander  expresses  the  conviction  "that  the 
poisonous  effect  of  Bordeaux  mixture  is  always  brought  about  thru 
the  activity  of  the  secretory  organs."  He  expresses  the  opinion  that 
the  injuries  observed  on  peach  and  sunflower  are  of  the  same  nature 
as  those  observed  upon  beans.  Altho  as  he  says,  the  possibility  of 
peach  leaves  secreting  a  liquid  has  not  yet  been  proved.  Third,  "Small 
quantities  of  copper  salts  are  dissolved  by  rain  and  dew  and  penetrate 
the  epidermis  into  the  interior  of  the  leaf.  Because  of  the  slight 
solubility  of  copper  in  Bordeaux  mixture  this  rarely  takes  place." 

The  statements  and  suggestions  regarding  the  causes  operating  to 
bring  into  solution  the  copper  of  Bordeaux  mixture  deposited  on  the 
leaves,  as  given  by  the  authors  quoted  above  are  interesting  and  help- 
ful, but  are  not  supported,  at  least,  so  far  as  apple  tree  foliage  te  con- 
cerned, by  proof  that  can  be  accepted  as  the  final  conclusion  of  the 
matter.  It  seems  possible  that  atmospheric  conditions,  meteoric 
waters,  carbon  dioxide,  and  leaf  secretions  may  all  be  concerned  in 
solution  of  the  copper.  The  results  of  many  recorded  experiments 
and,  of  our  own  experiments  here,  all  show  great  dependence  upon  at- 
mospheric conditions.  This  term,  atmospheric  conditions,  is  a  very 
convenient  cloak  for  meagre  information  regarding  specific  causes  af- 
fecting solubility  of  copper,  but  it  is  altogether  too  indefinite  and  is 
separable  into  too  many  factors  to  indicate  accurate  and  definite  knowl- 
edge of  the  really  active  agent  or  agencies. 

Schander,   R.     Landwirtschaftliche  Jahrhucher  33,   1904,   p.    526. 


228  BULLETIN  No.  135  [Afa.v 

The  term  "meteoric  waters"  is  likewise  a  composite  embracing 
not  only  the  waters,  but  the  materials  carried  in  solution  and  the  rela- 
tions to  one  or  more  of  a  dozen  different  atmospheric  conditions.  Rain 
water  collected  in  a  cistern  and  artificially  applied,  gives  very  different 
results  from  those  following  natural  rain  and  there  are  wide  differences 
in  the  observed  action  of  different  natural  rains  upon  Bordeaux  mix- 
ture. 

In  less  degree  but  no  less  certainly,  there  is  something  of  the  com- 
posite in  carbon  di6xide  as  a  cause  of  solution  of  the  copper  of  Bor- 
deaux mixture,  at  least  there  is  need  of  more  definite  information  re- 
garding its  action  in  relation  to  other  factors  with  which  it  is  associ- 
ated. 

It  is  not  known  whether  apple  leaves  give  off  secretions  having 
solvent  action  on  copper  hydroxide.  Experiments  thus  far  undertaken 
have  not  warranted  any  definite  conclusion  and  the  matter  is  to  be 
given  further  study.  In  attempting  to  account  for  the  presence  of  cop- 
per in  solution,  in  waters  that  have  dripped  from  sprayed  leaves,  and 
in  which  free  lime  is  present  in  quantity,  it  has  been  found  that  these 
waters  contain  organic  matter.  According  to  Ostwald1  adding  lime  in 
excess  to  cupric  salts  in  the  presence  of  certain  organic  compounds  e.g. 
sugar,  tartaric  acid,  glycerine,  etc.,  forms  certain  complex  copper  com- 
pounds which  are  not  precipitated  from  solution  by  alkalies.  In  cer- 
tain laboratory  experiments,  organic  matter,  in  the  form  of  apple 
leaves  macerated  in  water,  added  in  small  quantity  to  a  solution  of 
copper  sulphate,  used  in  making  Bordeaux  mixture,  prevented  complete 
precipitation  of  the  copper.  The  organic  matters  present  in  the  drip 
varied  in  quantity  in  different  waters.  The  specific  compounds  have 
not  been  determined  nor  has  the  origin  been  ascertained.  But,  from 
some  of  the  attending  circumstances  it  is  thought  possible  that  secre- 
tions from  leaves  may  have  contributed.  Further  experiments  are  to 
be  made. 

PENETRATION  OF  COPPER  INTO  LEAF  TISSUES 

There  are  differences  of  opinion  regarding  the  manner  in  which 
copper  brought  into  solution  on  leaf  surfaces  transmits  the  toxic  influ- 
ence that  kills  the  protoplasm  of  the  cells  within  limited  areas.  The 
view  most  "commonly  held  is  that  water,  holding  copper  in  solution, 
penetrates  the  cells  by  osmosis  or  by  a  process,  of  imbibition  and  thus 
by  direct  contact  kills  them.  According  to  this  theory  the  copper  is 
locked  in  the  dead  cells  and  does  not  spread  through  the  leaf  as  would 
some  other  poisons.  This  view  of  penetration  is  upheld  by  Millardet 
and  Gayon2,  Patrigeon3,  Aderhold4,  Schander5,  and  others.  Opposed  to 
this  view,  is  the  theoretical  conception,  first  advanced  by  Rumm8  and 
supported  by  Frank  and  Kruger7,  and  by  Zucker  that  poisonous  action 


Ostwald.      The    Principles   of    Inorganic    Chemistry.      Trans,    by    Findlay,    1902,    pp.    532-643. 

2Millardet  and  Gayon,  Jour.  d'Agr.  Prat.  Jan.  27,   1887,  p.   126;  Feb.  23,  p.   159. 

3Dr.   G.   Patrigeon,  Jour.   d'Agr.   Prat.   May  5,    1887,   p.   641. 

«R.  Aderhold,  Jahrsber  Angew.   Bot.   1,   1903,  pp.   26-30. 

6R.  Schander,  Landwirtschaftliche  Jahrbucher,  33,  1904,  p.  540. 

8C.  Rumm,  Ber.  Deut.  Bot.  Ges.  Band  XI   (1893),  pp.  79-93. 

'Frank  and   Kruger,   Ber.   Deut.   Bot.   Ges.    Band.    XII    (1894),   pp.    8-11. 


1909]  BORDEAUX  MIXTURE  229 

results  from  contact  without  penetration.  Rumm  calls  the  action  chem- 
otactic,  and  ascribed  it  to  electrical  attraction  between  cell  protoplasm, 
and  the  coating  of  Bordeaux  deposited  on  the  leaves.  This  theory  of 
action  by  electrical  attraction  is  based  on  Nageli's  work  on  Spirogyra, 
the  chlorophyll  bands  of  which  were  broken  up  by  the  near  proximity 
of  metallic  copper,  thru  the  action  of  some  force  to  which  the  name 
oligodynamic  was  applied.  "Zucker1  found  plants  treated  with  Bor- 
deaux more  resistant  to  etiolation  than  untreated  plants,  and  partially 
etiolated  plants  placed  under  treatment  developed  the  normal  green 
color.  He  regards  the  action  as  an  electrical  stimulus  and  "since  in  all 
plants  more  or  less  weak  electrical  currents  are  produced  by  the  motion 
of  the  water  in  the  capillary  spaces,  it  is  reasonable  that  the  deposition 
of  a  strongly  electro-positive  substance,  like  copper  hydroxide,  upon 
the  leaves  should  be  capable  of  intensifying  the  plant  currents  with 
stimulating  effect  upon  the  activity  of  the  protoplasm."  Aderhold  and 
Schander  hold  the  stimulating  effect  of  copper  to  be  only  slight  and  of 
rare  occurrence.  Where  it  does  occur,  they  attribute  it  to  penetration 
of  the  cells  by  the  copper,  with  direct  action  upon  the  cells,  and  the 
more  common  injurious  effect  is  attributed  to  the  accumulation  of  cop- 
per, in  quantity  sufficient  to  kill  the  cells. 

The  supporters  of  Nageli's  theory  of  oligodynamic  action  appear 
to  have  accepted  it,  because  of  their  inability  to  demonstrate  the  pres- 
ence of  copper  within  the  plant  cells.  Those  who  oppose  the  theory 
have  had  no  better  success  in  demonstrating  the  presence  of  copper  in 
the  cells,  but  hold  to  the  theory  of  penetration  by  the  copper  as  more 
probable  than  the  chemotactic  action  as  proposed  by  Rumm.  Schan- 
der2 credits  .Rumm  with  the  statement  that  the  amount  of  copper  neces- 
sary to  produce  destructive  action  on  the  cells  is  so  small  that  it  is  not 
possible  to  detect  it  and  adds  "An  assertion  that  is  difficult  to  refute 
and  equally  difficult  to  prove."  Millardet  and  Gayon3  were  the  first  to 
investigate  the  behavior  of  copper  on  leaves,  and  their  conclusions  are 
drawn  from  the  results  of  numerous  experiments.  In  one  series  of 
experiments,  grape  leaves  were  sprayed  with  200  grams  of  a  solution  of 
copper  sulphate,  2.5  grams  to  100  grams  of  water,  and,  after  being  sub- 
jected, during  one  week  to  rains  giving  a  precipitation  of  26  milli- 
meters, were  gathered  and  divided  into  two  lots.  One  lot  was  washed 
ten  times  with  water,  the  other  an  equal  number  of  times  with  dilute 
hydrochloric  acid.  Each  lot  of  water  was  analyzed,  and  the  amount  of 
contained  copper  determined.  Then  the  lots  of  leaves  were  incinerated 
and  the  copper  in  the  ash  ascertained.  Leaves  washed  with  water  gave 
58.3  percent  of  the  total  copper  in  the  ash,  those  washed  with  acid  6.1 
percent.  They  conclude  from  this  experiment  that  "the  copper  sulphate 
deposited  on  the  leaves,  in  the  form  of  very  dilute  solution,  and,  in  very 
slight  quantity,  is  absorbed  for  the  most  part,  and  very  rapidly,  so  that 
the  abundant  rains  are  unable  to  remove  it  from  the  leaves."  In  a 
later  series  of  experiments  these  authors  digested  grape  leaves  in  sul- 


'Quoted  from   Schander,  p.  539. 

2L.   C.,  p.  540. 

'Jour.    d'Agr.    Prat.    Jan.    27,    1887,    pp.    125-126. 


230  BULLETIN  No.   135  [May 

phuric  acid  for  24  hours,  destroying  all  tissue  except  the  cuticle.  The 
remains  were  collected,  washed  free  from  acid,  by  prolonged  macera- 
tion in  water,  and  when  neutral,  were  placed  in  100  c.c.  of  copper  sul- 
phate solution,  containing  10  milligrams  of  copper.  After  24  hours, 
the  liquid  was  filtered,  and  the  cuticle  placed  in  distilled  water.  Finally 
the  particles  of  cuticle  were  again  collected,  dried,  incinerated,  and  cop- 
per determinations  made,  by  the  electrolytic  method,  both  for  the  ash, 
the  original  copper  sulphate  solution,  and  the  distilled  water  in  which 
the  particles  were  last  soaked.  The  copper  recovered  was  as  follows : 

In  solution  where  the  cuticle  was  soaked  24  hours 0.1  mg. 

Jn  distilled  water  where  cuticle  was  soaked 0.0  mg. 

In  ashes  of  the  cuticle 9.8  mg. 

Total  copper  recovered 9.9  mg. 

Following  this,  an  experiment  was  made,  to  test  the  rate  of  ab- 
sorption. From  the  two  experiments  the  authors  conclude  as  follows :' 
"These  two  last  experiments  show  with  what  rapidity  the  copper  is 
absorbed  by  the  cuticle,  since  after  only  half  an  hour,  half  of  the  cop- 
per of  the  liquid  had  been  absorbed  and  after  one  and  one  half  hours 
in  one  of  the  experiments  the  absorption  of  this  metal  was  completed." 
Certain  other  experiments,  designed  to  test  the  extension  of  the  influ- 
ence of  the  absorbed  copper  beyond  the  cuticle,  and  in  which  inocula- 
tions with  spores  of  Peronospora  were  made  on  the  lower  surfaces  of 
sprayed  leaves,  gave  results  from  which  the  authors  conclude  that  the 
copper  absorbed  by  the  cuticle  extends  its  influence  deep  enough  into 
the  leaf,  to  protect  in  great  part  from  infestation.  Finally,  from  all 
the  experiments  this  conclusion  is  drawn —  "It  seems  certain  that  the 
copper  once  absorbed  by  the  leaf  is  acquired  by  it  in  definite  manner 
and  can  no  longer  depart  from  it.  Not  only  is  it  fixed  by  the  cuticle 
of  the  upper  face,  making  that  absolutely  invulnerable  to  the  parasite, 
but  it  is  diffused  deeply  enough  in  the  tissues  to  constitute  a  means  of 
protection  to  the  lower  surface  of  the  leaf,  if  not  sufficient,  it  can  at 
least  prevent  development  of  the  parasite  in  an  appreciable  degree." 

Absorption  of  copper,  by  the  cuticle  of  grape  leaves,  appears  to  be 
demonstrated  by  these  experiments,  but  the  conditions  surrounding  the 
experiments  are  so  far  removed  from  normal  that  it  may  be  questioned 
whether  like  absorption  occurs  under  the  ordinary  practice  of  spraying 
and  whether  Bordeaux  mixture  would  act  in  the  same  manner  as  did 
the  copper  sulphate  solution,  which  can  not  be  used  in  practice,  be- 
cause of  its  injurious  action  upon  foliage.  The  solution  used  in  the 
experiments — 2l/2  grams  per  1000  or  1 :400 — was  beyond  the  limit  of 
safe  use  on  grape  vines,  according  to  these  authors,  who  formulate  as 
a  law  the  proposition  that3  "All  liquid  containing  more  than  one  half 
thousandth  ( 1 :2000)  of  copper  in  solution  is  dangerous  for  the  grape 
vine."  The  statement  that  copper,  absorbed  by  the  cuticle,  is  acquired 
permanently,  can  not  depart  from  the  leaf,  and  renders  it  invulnerable 
is  also  open  to  question.  If  the  statement  were  true  the  protection 

1Millardet  and  Gayon.     Jour.  d'Agr.  Prat.  Feb.  23,  1887,  p.   159. 
*Millardet  and  Gayon.     Jour.   d'Agr.   Prat.   Feb.   23,   1887,  p.   162. 
3Millardet   and  Gayon.     Jour.   d'Agr.   Prat.   May  26,   1887,   p.   729. 


1909]  BORDEAUX  MIXTURE  231 

would  extend  thru  the  season,  preventing  infection  by  fungi  that 
develop  in  late  summer.  It  is  well  known  that  apple  trees,  heavily 
sprayed  in  spring  and  early  summer,  gradually  lose  the  copper  from  the 
leaves  and,  in  seasons  of  normal  rainfall,  are  readily  susceptible  to  at- 
tacks of  species  of  Phyllosticta  and  often,  when  conditions  are  favor- 
able, to  renewed  development  of  Fusicladium.  These  attacks  can  be 
prevented  by  renewed  applications  of  Bordeaux  mixture,  but,  in  the 
absence  of  late  applications,  the  leaves  are  attacked.  From  this  it 
appears,  that  there  can  be  no  copper  held  in  the  cuticle  or,  at  least,  not 
enough  to  prevent  infection  by  fungi  which  naturally  begin  or  renew 
development  in  late  summer. 

Rumm1  dwells  upon  the  darker  color  and  the  more  robust  charac- 
ter of  sprayed  leaves,  and,  from  examinations  under  the  microscope, 
decides  that  the  deeper  color  is  due  to  increase  in  the  number  of  chloro- 
phyll grains.  From  47  measurements  of  the  thickness  of  grape  leaves, 
he  finds  a  gain,  in  favor  of  the  sprayed  leaves,  over  unsprayed  leaves, 
ranging  from  2.17  to  16.31  micromillimeters  (p.  84).  Regarding 
causes  of  the  stimulating  effects  observed,  Rumm  suggests  two  possi- 
bilities— "Either  remains  of  the  sprayed  salts  are  taken  up  thru  the 
epidermis  by  the  leaf,  resulting  in  chemical  changes  which  appear 
sooner  or  later  in  the  above  considered  physiological  changes  or  the 
materials  only  adhere  firmly  to  the  cuticle,  remain  on  the  whole  un- 
changed and  act  only  by  their  presence,  that  is,  exert  an  influence  on 
the  life  activities  of  the  plant,  unexplained  up  to  this  time,  similar  to 
the  influence  exerted  by  light,  gravity,  etc."  (1.  c.  p.  85). 

In  order  to  test  these  alternatives,  grape  leaves,  sprayed  with  Bor- 
deaux mixture  were  washed  with  dilute  muriatic  acid,  until  the  wash 
waters,  when  tested  by  the  spectroscope,  gave  no  copper  lines.  Then 
the  leaves  were  incinerated,  the  ash  dissolved  and  tested  for  copper 
by  the  spectroscope.  No  evidence  of  the  presence  of  copper  appeared 
and  from  this  result  it  was  concluded,  "that  in  our  experiments  it  was 
highly  probable  that  copper  had  not  been  taken  up  by  the  leaves  in 
quantity  that  could  be  indicated  by  the  spectroscope."  (1.  c.  p.  88). 
The  final  conclusion  reached  by  Rumm  is  expressed  as  follows :  "It  is 
highly  probable  that  the  increase  in  the  formation  of  chlorophyll  de- 
pends upon  a  chemotactic  attraction  which  takes  place' without  absorp- 
tion of  the  material."  (1.  c.  p.  92). 

In  an  interesting  series  of "  experiments  recorded  by  Schander2 
leaves  of  a  variety  of  plants  were  used.  Each  leaf  was  injured  on  half 
its  surface  by  needle  pricks,  then  the  leaves  were  sprayed  with  copper 
sulphate  solutions  in  various  dilutions.  Apple,  pear  and  grape  leaves 
showed  no  injury  from  a  1 : 100,000  solution  where  the  epidermis  had 
not  been  injured,  but  were  considerably  injured  where  the  surfaces  had 
been  pricked.  The  author  concludes  "that  the  epidermis  of  these  leaves 
is  capable  of  preventing  the  penetration  of  copper  compounds,  but  that 
the  copper,  having  once  penetrated,  behaves  towards  the  protoplasm  of 
the  leaf  cells,  in  the  same  manner  as  towards  the  cells  of  algae  and 

^umm,   C.    Ber.   Dent.   Bot.    Ges.    Band   XI,   1893,   pp.   83-85. 
"Schander,   R.      Landwirtschaftliche  Jahrbucher '33    (1904),  p.   544. 


232  BULLETIN  No.   135  [May 

fungi,  and  can  injure  the  protoplasm  in  very  dilute  solutions."  (1.  c.  p. 
546). 

The  only  proof  of  penetration  that  can  be  accepted  as  absolute,  is 
demonstration  of  the  presence  of  copper  within  the  tissues  of  leaves 
that  have  been  sprayed  with  Bordeaux  mixture.  This  demonstration 
appears  not  to  have  been  made,  and  until  it  is  made,  it  is  only  possible 
to  state  probabilities  as  estimated  from  observed  facts.  Statements  to 
the  effect  that  penetration  occurs,  followed  by  accumulation  in  cuticu- 
larized  cell  walls,  do  not  appear  to  rest  on  sufficient  foundation  of  fact 
and  are  not  in  harmony  with  the  well  established  fact  that  extremely 
small  amounts  of  copper  are  poisonous  to  cell  protoplasm.  If  such 
accumulation  occurs,  it  can  hardly  apply  to  other  than  very  minute 
quantities,  unless  it  be  thru  chemical  changes,  which  form  new  com- 
pounds, inocuous  to  the  protoplasm  of  living  cells.  Again,  the  pres- 
ence of  accumulations  of  copper  in  the  cuticle  should  prevent  infection 
by  fungi  as  long  as  the  leaf  lives.  But,  as  has  already  been  stated, 
leaves  sprayed  early  in  the  season  become  susceptible  to  infection  in 
late  summer,  unless  the  protective  spray  is  renewed. 

On  the  upper  surface  of  each  of  several  healthy  apple  leaves,  on 
one  year  old  grafted  trees  growing  in  ten  inch  pots,  were  placed  in 
single  drops  solutions  of  copper  sulphate  ranging  from  1 :100  to 
1 :1000.  The  leaves  were  so  adjusted  that  they  could  be  brought 
within  the  focus  of  the  lens  for  convenient  examination.  The  drops 
soon  evaporated,  leaving  small  masses  of  crystals.  These  were  again 
brought  into  solution  by  adding  drops  of  rain  water.  This  was'  re- 
peated twice,  or,  sometimes,  three  or  four  times  each  day,  for  two 
weeks  and  frequent  examinations  were  made.  In  no  case,  did  injury 
to  the  leaves  result,  and  it  was  concluded  that,  under  laboratory  condi- 
tions, the  uninjured  epidermis  of  apple  leaves  was  not  permeable  by 
copper  sulphate  solutions. 

At  the  same  time,  other  leaves,  arranged  in  the  same  way,  were 
treated  with  the  same  solutions  applied  in  drops  over  more  or  less 
minute  pricks  or  abrasions  of  the  epidermis.  These  applications  were 
uniformly  followed  by  injury  appearing  first  as  reddish  or  purplish 
discolorations,  which  soon  became  brown.  It  is  assumed,  that  break- 
ing the  impermeable  epidermis  established  connection  between  the  drop 
and  the  exuding  cell  sap  and  that  thru  this  channel  the  copper  solu- 
tion penetrated  and  killed  the  cells. 

^The  brown  spots  were  not  of  equal  size,  nor  were  they  in  all  cases 
co-extensive  with  the  abrasions,  or,  with  the  areas  covered  with  the 
drops  applied.  Compared  with  brown  spots,  resulting  from  spraying, 
on  the  leaves  of  orchard  trees,  no  distinguishing  characteristics  ap- 
peared. They  were  identical  in  appearance  and  exhibited  the  same 
variations  in  size  and  form.  If  the  assumption  of  penetration  of  cop- 
per is  warranted,  in  the  case  of  spots  originating  in  abrasions,  there  is 
equal  reason  for  assuming  penetration,  in  the  case  of  the  spots  on 
leaves  of  orchard  trees ;  altho  the  conditions,  making  penetration 
possible,  cannot  be  stated. 


1909]  BORDEAUX  MIXTURE  233 

Finally,  altho  actual  presence  of  copper  in  the  dead  cells  has  not 
been  proved,  numerous  observations  have  led  to  a  conviction,  strength- 
ened by  the  results  of  experiments,  that  brown  spotting  following 
applications  of  Bordeaux  mixture  is  due  to  the  death  of  leaf  cells,  and 
that  this  destruction  of  leaf  cells  is  caused  by  the  poisonous  action  of 
copper  in  solution  which  penetrates  to  them.  The  cause  or  causes  of 
conditions  making  such  penetration  possible,  are  still  open  to  investiga- 
tion. Out  of  the  great  mass  of  anomalous,  often  contradictory,  re- 
sults, that  have  accumulated,  it  is  yet  possible  to  frame  a  course  that 
will  lead  to  solution  of  those  matters  that,  at  the  present  time,  are 
obscure  and  not  well  understood.  The  two  things  that,  in  the  writer's 
view,  stand  out  most  prominently  as  promising  phases  of  the  investi- 
gation are — • 

First.  A  line  of  experimentation  designed  to  isolate,  as  far  as  is 
possible,  and  subject  to  separate  tests,  each  of  several  factors  included 
under  the  term  atmospheric  conditions. 

JSecond.     The  physical  condition  of  leaves  at  the  time  of  spraying. 

The  importance  of  this  second  phase  has  been  suggested  by  ob- 
servations made  in  the  field.  From  inquiry  into  the  circumstances 
surrounding  wide  differences  in  the  amount  of  injury  inflicted  in  dif- 
ferent orchards,  it  appears  that,  in  some  cases,  differences  in  materials 
and  methods  do  not  account  for  differences  in  injury.  It  also  appears 
that,  in  some  cases,  it  is  possible  to  correlate  the  degree  of  injury  and 
condition  of  foliage.  Orchards  receiving  the  best  care  have  least  in- 
jury. Orchards  of  low  vitality  induced  by  general  lack  of  care  and  by 
the  ravages  of  insects  and  diseases,  which  general  conditions  tend  to 
harbor  and  encourage,  suffer  most  injury.  It  has  frequently  been  ob- 
served that  late  spraying  causes  more  injury  than  early  spraying;  and 
that  old  leaves  are  more  susceptible  to  injury  than  young  leaves.  It 
may  appear  anomalous  that  young  leaves  with  thin,  slightly  cuticular- 
ized  epidermis,  should  be  more  resistant  than  older  leaves  with  fully 
developed  cuticle.  But  it  is  believed  that  such  is  the  case;  not  be- 
cause of  the  thinner  epidermis,  but  because  of  greater  freedom  from 
abrasions  that  allow  penetration  of  the  copper  as  it  becomes  soluble. 
Old  leaves  have  been,  for  a  longer  time,  subject  to  the  attacks  of  the 
numerous  insects  that  infest  orchards  that  are  not  given  good  care  and 
are  thus  made  susceptible  to  injury. 

FUNGICIDAL  ACTION  OF  BORDEAUX  MIXTURE 

The  value  of  Bordeaux  mixture  as  a  fungicide  rests  in  the  prophy- 
lactic action  of  the  contained  copper.  It  has  little,  if  any,  curative 
power.  It  does  not  check  the  growth  of  fungi,  vegetating  within  plant 
tissues,  but  simply  prevents  germination  of  spores  or  arrests  growth 
of  germ  tubes,  and  in  this  manner,  checks  spread  of  infection. 

It  is  important  that  this  point  be  understood  and  that  application 
of  remedies  be  governed  accordingly.  If  attack  of  a  fungus  is  threat- 
ened, it  is  necessary  that  the  mixture  be  applied  to  the  susceptible 
plants  in  advance  of  the  appearance  of  the  fungus.  Early  application 
with  the  one  aim  of  defense,  is  infinitely  to  be  preferred  to  later  appli- 
cations, intended  to  check  ravages  already  begun. 


234  BULLETIN  No.  135  [May 

Simple  solutions  of  copper  sulphate  are  more  effective  as  fungi- 
cides than  is  Bordeaux  mixture,  but  their  poisonous  action  on  foliage 
puts  a  ban  on  their  use.  Millardet  and  Gayon1  made  many  experiments 
with  solutions  of  various  strengths  and  they  cite  the  experiences  of 
other  investigators.  The  results  all  show  that  even  very  dilute  solu- 
tions are  not  safe  to  use  on  foliage.  From  numerous  experiments,  at 
this  Station,  with  solutions  of  copper  sulphate,  it  is  concluded  that  such 
solutions  have  no  adhesive  qualities,  and  that  the  limits  of  safety  to 
foliage  require  dilution  that  renders  the  solutions  inefficient  as  fungi- 
cides. 

In  the  early  stages  of  their  work  with  Bordeaux  mixture,  Mil- 
lardet and  Gayon  studied  the  action  of  various  copper  solutions  upon 
the  conidia  and  zoospores  of  the  grape  mildew  (Peronospora  viticola',, 
in  order  to  determine  the  degree  of  concentration  necessary  to  prevent 
infection.  This  was  found2  to  be,  for  a  lime  solution  1 :10000,  for  a 
sulphate  of  iron  solution  1 :100000  and  for  a  copper  sulphate  solution 
2  to  3:10  000  000.  Other  investigators  have  made  similar  tests,  prin- 
cipally with  spores  of  the  various  rusts  and  smuts  of  cereals,  and  all 
show  that  extremely  dilute  solutions  are  effective  in  preventing  germin- 
ation and  growth.  Spores  of  different  fungi,  however,  show  different 
degrees  of  resistance,  all  do  not  behave  alike  in  a  solution  of  given 
strength.  For  example  spores  of  Penicillium  will  germinate,  and  my- 
celium develop  with  great  vigor  in  solutions  that  effectively  prevent 
germination  of  spores  of  Peronospora  viticola;  the  downy  mildew  of 
the  grape. 

In  several  tests  made  here,  with  spores  of  the  apple  scab  fungus 
(Fusicladium  dentriticum)  a  considerable  degree  of  resistance  has  been 
found.  Solutions  perfectly  effective  against  grape  mildew  do  not  have 
even  a  retarding  action  on  growth  of  spores  of  the  scab  fungus.  In 
solutions  1:10000  germination  was  effectively  prevented.  Solutions 
1 :25  000 ;  1 :50  000  and  1 :75  000  did  not  entirely  prevent  germination, 
but  did  retard  growth  of  the  germ  tubes  in  proportion  to  the  degree  of 
concentration. 

In  a  solution  1 : 100  000,  germination  was  more  abundant  than  in 
any  of  the  stronger  solutions,  but,  in  comparison  with  the  check 
mount,  some  retardation  of  growth  was  observed  here.  In  still  weaker 
solutions,  germination  was  as  free  and  growth  as  strong  as  in  the  con- 
trol mounts.  In  the  stronger  solution  1:10000  penicillium  grew  with 
apparently  undiminished  vigor. 

YELLOWING  OF  LEAVES 

The  causes  which  produce  yellowing  of  the  leaves  of  apple  trees 
are  obscure  and  not  well  understood.  From  observations  extending 
over  five  seasons,  it  is  thought  to  be  certain  that  there  are  several 
causes  which  may  operate  singly,  or  two  or  three  together  in  certain 
cases.  The  trouble  may  appear  at  any  time  between  full  expansion 
of  leaves  and  frost,  but  has  been,  usually,  more  in  evidence  during 

»Millardet  and  Gayon,  Jour.   d'Agr.   Prat.   May   26,   1887,  p.   729. 
•Millardet  and  Gayon,  Jour.  d'Agr.  Prat.  Nov.  12,  1885,  p.  709. 


1909]  BORDEAUX  MIXTURE  235 

June  and  July,  than  earlier  or  later.  Very  commonly,  attacks  of  yel- 
lowing have  been  intermittent,  occurring  two  or  more  times  in  the 
course  of  a  season.  During  the  last  two  seasons,  this  trouble  was  not 
as  severe  as  for  1904,  1905  and  1906.  From  1903  to  1906,  there  ap- 
peared to  be  a  gradual  augmentation  of  yellowing  and  in  view  of  the 
marked  diminution  in  1907,  and  the  still  less  amount  observed  in  1908, 
the  hope  has  been  expressed  that  a  period  of  immunity  may  be  at 
hand.  It  hardly  seems  probable,  however,  that  there  is  any  period- 
icity in  connection  with  the  trouble.  If  there  should  be,  it  would  over- 
turn many  expressed  theories,  relieve  Bordeaux  mixture,  and  the  gen- 
eral practice  of  spraying  from  an  obligation  which  in  the  minds  of 
many  men  it  now  carries  and  lead  investigation  into  other  channels. 

The  conditions  attending  yellowing  in  cases  of  intermittent  at- 
tacks, have  been  closely  observed,  and  effort  made  to  establish  direct 
relation  between  these  recurrent  appearances  and  weather  conditions, 
but  without  marked  success.  If  the  sudden  appearance  of  many  yel- 
low leaves  occurred  repeatedly  in  connection  with  either  wet  or  dry 
periods,  this  would  be  good  evidence  of  causal  relation  to  soil  moisture, 
but  such  is  not  the  case.  One  attack  may  come  during  a  dry  period, 
another  in  time  of  excessive  moisture  and  still  another  when  moisture 
conditions  are  normal,  or,  the  several  attacks  of  a  season  may  all  come 
at  times  when  it  is  impossible  to  trace  any  relation  to  either  shortage 
or  excess  of  moisture.  Of  two  contiguous  orchards,  apparently  alike 
in  soil  and  treatment,  one  may  develop  an  abundance  of  yellow  leaves 
at  a  time  when  the  other  has  none.  Occurrences  of  this  nature  tend 
rather  to  obscure  than  to  make  clear  the  true  causes.  In  one  case,  an 
orchard,  deeply  cultivated,  displayed  an  unusually  large  number  of 
yellow  leaves.  Examination  disclosed  the  fact  that  the  cultivation  had 
destroyed  great  quantities  of  feeding  rootlets,  enough  to  seriously 
affect  the  trees.  That  this  disturbance  of  rootlets  caused  the  outbreak 
of  yellow  leaves  seems  reasonable,  but  had  only  one  portion  of  the  or- 
chard been  so  treated  with  the  result  of  yellow  leaves  on  that  portion 
while  there  were  none  on  the  uncultivated  portion,  there  would  have 
been  better  basis  for  a  definite  conclusion.  However,  orchards  in  the 
neighborhood,  that  were  not  cultivated  did  not  at  this  time  develop 
yellow  leaves.  The  fact  that  a  considerable  number  of  well  sprayed 
orchards  have  been  more  or  less  seriously  affected  with  yellowing  of 
leaves  has  served  as  basis  for  an  opinion,  current  among  orchard  own- 
ers, that  Bordeaux  mixture  is  responsible  for  the  trouble.  This  often 
expressed  opinion  has  been  one  of  the  factors  determining  the  charac- 
ter of  experiments  undertaken  by  the  Station.  These  experiments 
have  been  numerous  and  some  of  them  are  not  yet  concluded.  From 
the  work  thus  far  done,  it  may  be  stated,  that  no  conclusive  evidence 
has  been  secured,  indicating  Bordeaux  mixture  as  a  cause  of  yellow- 
ing. Results  for  the  last  two  seasons  were  negative,  because  of  the 
almost  entire  absence  of  yellowing.  In  1906,  a  few  of  the  trees  on 
plats  sprayed  with  well  made  Bordeaux  mixture,  lost  each  a  few  leaves 
by  yellowing,  but  the  number  was  insignificant,  and  as  the  control  trees 
lost  much  greater  numbers,  at  the  same  time,  it  appears  that  the  action 


236  BULLETIN  No.  135 

of  the  Bordeaux  was  rather  in  the  direction  of  retarding  or  check- 
ing than  in  promoting  the  trouble.  In  one  instance,  in  1905,  a  por- 
tion of  an  orchard  sprayed  by  the  department,  was  entirely  free 
from  yellow  leaves,  while  adjoining  portions  sprayed  at  the  same  time 
by  the  owner,  were  seriously  affected.  Bordeaux  mixture  was  used  by 
both ;  that  used  by  Station  men  was  properly  prepared ;  that  used  by 
the  owner  was  neither  well  made  nor  well  applied.  There  was  gross 
carelessness  at  every  stage  of  the  process  and  the  unfortunate  results 
were  not  unexpected. 

In  one  orchard  under  observation  three  spring  applications  of 
Bordeaux  were  made ;  the  last  on  May  23.  The  foliage,  except  for  a 
few  brown  spots  on  some  of  the  leaves,  was  perfectly  healthy  until 
June  28,  on  which  date  yellow  leaves  began  to  appear.  These  in- 
creased in  number,  and  July  1,  were  recorded  as  numerous  on  Whitney, 
Oldenburg,  Grimes  Golden,  and- especially  on  two  trees  of  Sweet  Belle- 
flower.  Ben  Davis  and  Winesap  had  yellow  leaves  in  much  smaller 
numbers,  very  few  on  each  tree.  Light  rains  fell  on  July  1  and  2,  a 
heavier  one,  followed  by  a  strong  wind,  on  the  evening  of  July  3.  July 
4,  all  yellow  leaves  had  fallen  from  the  trees,  and  no  more  were  seen 
until  late  in  the  month  and  then  only  a  few.  At  the  time  of  this  at- 
tack of  yellowing,  apple  trees  in  the  neighborhood  that  had  not  yet 
been  sprayed  had  as  many  yellow  leaves  as  had  the  sprayed  trees  re- 
ferred to,  and  certain  ornamental  and  forest  trees  lost  many  leaves  in 
the  same  way,  and  apparently  from  the  same  cause.  Yellow  leaves  were 
particularly  abundant  on  certain  black  cherry  trees,  while  other  trees 
of  the  same  species  were  free  from  them.  Tulip  tree,  basswood,  syca- 
more, and  elm  trees  were  also  observed  to  have  many  yellow  leaves,  all 
of  which  fell  at  the  same  time  as  the  yellow  apple  leaves.  In  view  of 
these  observations,  it  is  difficult  to  assign  any  connection  between  the 
spraying  done  in  spring  and  the  yellow  leaves  appearing  in  June. 

While  no  direct  and  positive  connection  could  be  established  be- 
tween spraying  with  Bordeaux  mixture  and  the  yellowing  of  leaves, 
results  with  copper  sulphate  solution  were  quite  different.  Very  good 
evidence  was  obtained  showing  that  simple  solutions  of  the  copper  salt 
do  cause  yellowing.  A  plat  of  eight  trees  was  sprayed  with  a  solution 
of  copper  sulphate  1 :100  in  June,  following  three  spring  applications 
of  the  Bordeaux-Paris  green  mixture.  Except  for  a  few  brown  spots, 
the  foliage  was  in  excellent  condition  at  the  time  of  applying  the  solu- 
tion. The  day  after  spraying  with  the  copper  sulphate  almost  every 
leaf  was  more  or  less  brown  spotted,  and  the  green  parts  of  many 
leaves  exhibited  that  lighter  shade  of  green  which  precedes  yellowing. 
The  next  day  yellowing  was  well  advanced  and  leaves  began  falling. 
By  the  fourth  day,  the  ground  was  covered  with  yellow  leaves,  and 
many  more  were  falling.  It  was  estimated  that  more  than  half  the 
leaves  became  yellow  and  fell.  A  possible  relation  between  brown 
spotting  and  yellowing  is  suggested  in  the  fact  that  all  yellow  leaves 
had  also  brown  spots.  From  under  one  tree,  1000  yellow  leaves  were 
gathered  and  examined.  Every  one  was  more  or  less  brown  spotted. 
Many  leaves  on  the  same  tree,  that  were  marked  with  brown  spots,  did 


1909]  BORDEAUX  MIXTURE  237 

not  become  yellow,  and  no  relation  could  be  traced  between  yellowing 
and  the  amount  of  brown  spotting  on  individual  leaves.  Leaves  hav- 
ing only  one  or  two  small  brown  spots  became  yellow  as  often,  as  did 
those  in  which  half  the  area  was  brown. 

On  a  second  plat  sprayed  at  the  same  time  with  a  solution  of 
half  the  strength,  1  :200,  some  leaves  became  yellow,  but  probably  not 
more  than  one  fourth  as  many  as  on  the  plat  treated  with  the  stronger 
solution.  There  was  also  a  great  diminution  in  the  amount  of  brown 
spotting,  following  use  of  the  weaker  solution.  Adjoining  plats, 
which  received  only  the  three  earlier  applications  of  Bordeaux  mix- 
ture and  Paris  green  were  free  from  yellow  leaves. 

As  a  supplement  to  the  work  on  these  plats  sprayed  with  solutions 
of  copper  sulphate  and  as  a  means  of  obtaining  more  detailed  informa- 
tion, a  number  of  small  branches  were  diagramed,  treated  with  the 
same  solutions  and  examined  daily  for  the  development  of  injury. 
There  was  no  regularity  in  the  results  obtained.  In  all  cases,  the  first 
evidence  of  injury  was  seen  in  brown  spots.  Sometimes  these  spots 
appeared  very  soon  after  spraying  and  sometimes  not  for  several  days. 
They  varied  in  number  on  individual  leaves,  and  were  .of  all  sizes. 
Some  leaves  went  thru  the  stages  of  yellowing  and  dropped  off, 
but  the  number  thus  affected  was  not  excessive.  Grouping  those 
branches  treated  with  solutions,  1 :200  and  1 :100,  the  loss  from  yellow- 
ing was  found  to  be  25  percent ;  with  solutions  1 :300  and  1 :500  the 
loss  was  15^4  percent. 

Increase  in  strength  of  the  solution  increased  the  amount  of 
brown  spotting  much  more  rapidly  than  it  increased  the  yellowing  of 
leaves. 

COPPER  NOT  ABSORBED  THRU  BARK  OF  TRUNK  AND  BRANCHES 

In  spraying  with  Bordeaux  mixture,  the  trunks  and  branches  of 
trees  become  thoroly  coated,  and  this  coating  is  persistently  held 
for  long  periods.  This  fact  undoubtedly  suggested  a  question  which 
has  been  frequently  asked,  namely — "Is  copper  sulphate  absorbed  thru 
the  bark  in  sufficient  quantity  to  cause  yellowing  of  leaves"?  The 
outer  corky  layer  of  the  bark  of  trees  is  extremely  resistant  to  all  de- 
structive agencies  and  is  regarded  as  quite  impermeable  to  water  or 
other  liquids.  It  does  not  seem  probable  that  Bordeaux  mixture,  or 
copper  sulphate  solution,  could  exert  any  injurious  influence  on  leaves 
thru  this  channel,  but  in  order  to  test  the  matter  in  a  somewhat  definite 
way,  it  was  arranged  to  maintain  liquids  in  contact  with  the  bark,  for  a 
considerable  time  and  observe  results. 

Upright  branches  were  chosen,  whose  laterals  could  be  brought, 
by  means  of  bandages,  within  the  limits  of  the  bore  of  a  2^  inch  rub- 
ber tube.  A  piece  of  tubing,  15  inches  long,  was  then  slipped  down 
the  branch  and  the  lower  end  tied  tightly,  so  that  no  liquid  could  es- 
cape. The  tube  was  then  filled  with  liquid,  which  was  replenished  as 
often  as  was  necessary  to  keep  the  tube  full.  Four  tubes  were  pre- 
pared. Number  1  filled  with  copper  sulphate  solution  1:100;  number 
2  with  copper  sulphate  solution,  1  :500;  number  3  with  standard  Bor- 


238  BULLETIN  No.   135  [May 

deaux  mixture,  and  number  4,  with  distilled  water.  Examination  was 
made  daily  for  more  than  a  month.  No  injury  of  any  kind  could  be 
detected  and  the  test  was  then  discontinued.  The  bark  appears  to  be 
impervious  to  the  liquids  tested. 

COPPER  SULPHATE  SOLUTION  ABSORBED  THRU  WOUNDS 

The  tubes  were  now  adjusted  to  other  branches  and  filled  with  the 
same  liquids  freshly  prepared.  Within  the  tubes,  and  in  such  position 
as  to  be  emersed  in  the  liquids,  small  notches  were  cut  thru  the  bark 
into  the  alburnun.  The  precipitate  of  Bordeaux  mixture,  as  was  ex- 
pected, prevented  absorption  thru  the  cut,  and  this  tube  was  soon  dis- 
continued. Distilled  water  was  taken  in  freely,  without  any  injurious 
effect.  The  two  copper  sulphate  solutions  were  also  absorbed  thru  the 
cut  in  considerable  quantity.  These  tubes  were  filled  at  11:15  a.  m. 
July  5.  At  5  :00  p.  m.  of  the  same  day  the  effect  of  the  stronger 
solution,  1 :100,  was  apparent  in  a  brown  discoloration  which  was  con- 
fined to  the  midribs  and  their  branches.  No  effect  from  the  weaker 
solution,  1 :500,  could  be  detected  at  this  time.  When  examined  at 
9:00  a.  m.  July  6,  browning  could  be  detected  in  all  leaves  above  the 
point  of  attachment  on  both  branches.  Browning  was  in  a  much  more 
advanced  stage  on  the  branch  supplied  with  the  stronger  solution  than 
on  that  supplied  with  the  weaker  solution.  Many  leaves  were  entirely 
browned  and  some  of  these  were  variously  curled.  As  the  injury 
spread  from  the  vascular  bundles  the  tips  and  margins  of  the  leaves 
were  browned  first.  The  last  portions  to  lose  the  green  color  were 
longitudinal  strips  on  either  side  of  the  midrib.  The  morning  of  July 
7  the  effect  of  the  solutions,  on  leaves  of  branches  below  the  attach- 
ment began  to  appear.  The  injury  extended  gradually  and  irregularly 
as  regards  the  order  in  which  lateral  branches  were  affected  until  July 
20  when  observations  were  discontinued.  The  stronger  solution  had 
extended  its  influence  a  little  farther  than  the  weaker ;  otherwise  there 
were  no  differences  in  the  results.  There  was  at  no  time  any  evidence 
of  yellowing.  The  affected  leaves  all  became  brown.  They  died  and 
were  more  or  less  curled.  Some  persisted  and  some  fell.  This  ex- 
periment was  repeated  several  times  and  always  with  the  same  result. 

Attachment  of  the  tube  as  described  above  is  shown  in  Figure  1. 
This  illustration  is  from  a  photograph  of  a  branch  of  Whitney  apple 
used  in  one  of  the  later  experiments.  The  branch  as  shown  has  a 
length  of  about  12  feet.  The  lateral  to  which  the  tube  is  adjusted  is 
nearly  central.  The  solution  as  absorbed  killed  the  leaves  on  this  lat- 
eral first,  then  extended  its  influence  to  the  main  branch.  In  about  a 
week  all  leaves  on  the  branch  photographed  were  dead  and  many  had 
fallen.  A  solution  of  copper  sulphate  1  :500  was  used.  Attachment 
was  made  at  9  a.  m.  August  1.  At  6  p.  m.  the  same  day  no  injurious 
effect  was  apparent,  but  at  8  a.  m.  August  2  all  but  26  of  the  245  leaves 
on  the  lateral  above  the  tube  were  more  or  less  browned.  Extension 
of  injury  to  other  laterals  was  gradual  and  irregular. 

Following  this  same  line  of  work,  copper  sulphate  solutions,  of 
varying  degrees  of  concentration,  were  introduced  into  four  and  five 


1909] 


BORDEAUX  MIXTURE 


239 


year  old  trees  by  siphon  attachment  to  roots.  It  is  not  the  intention  to 
discuss  these  experiments  in  detail  at  this  time,  but  it  may  be  stated 
that  in  all  cases  injury  resulted  in  the  form  of  browning  of  leaves.  In 


FIG.    1.     Copper  sulphate  solution   1:500  absorbed  thru  wound  within  the   tube 
killed  all  the  leaves  on  this  branch.     From  photograph  August  8,   1906. 

no  case  did  yellowing  of  leaves  follow  absorption  of  solutions  thru 
the  roots.  The  time  of  appearance  and  rate  of  development  of  injury 
bore  a  distinct  relation  to  the  strength  of  the  solution  used,  but  it  was 
always  the  same  kind  of  injury,  a  browning  or  burning  of  the  leaves. 


240  BULLETIN  No.   135  [May 

Up  to  this  time  the  solutions  used  varied  between  1 :100  and 
1 :1000  and  all  produced  browning  of  leaves  with  no  symptoms  of  yel- 
lowing. It  was  then  thought  desirable  to  ascertain  the  limit  of  dilu- 
tion that  would  cause  browning,  the  quantity  of  solution  required,  the 
time  necessary  to  give  first  evidence  of  injury,  and  the  point  in  dilution, 
if  such  existed,  that  would  effect  just  the  degree  of  injury  that  would 
result  in  yellowing  instead  of  in  the  total  browning  of  the  leaves. 
During  July  and  August  1908  a  series  of  21  experiments  was  carried 
out.  The  results  obtained,  while  very  interesting  and  suggestive,  are 
not  conclusive  and  this  work  will  be  extended  the  present  season. 

INJECTION  OF  COPPER   SULPHATE   SOLUTION   1 :25000  FOLLOWED  BY 
YELLOWING  OF  LEAVES 

For  the  present,  brief  mention  of  the  results  from  one  tree  (Num- 
ber 14)  may  be  given.  A  bottle  with  capacity  for  holding  4  litres  of 
the  solution  was  supported  about  6  feet  above  the  ground  and  con- 
nected by  a  glass  siphon  with  a  hole  bored  into  the  alburnum  about  1 
foot  above  the  ground.  This  connection  was  thru  a  rubber  cork,  so 
adjusted  that  no  liquid  could  escape.  The  accompanying  Figure  2 
shows  this  tree  and  the  manner  of  attachment.  Graduations  were  ar- 
ranged on  the  outside  of  the  bottle  in  such  manner  that  readings  could 
be  made  of  the  approximate  amounts  of  solution  absorbed  within  a 
given  time. 

Copper  sulphate  solution  1 :25,000  was  used  for  this  tree.  The 
connection  was  made  at  2:00  p.  m.  August  31.  Between  2:00  p.  m. 
and  6 :00  p.  m.  3.3  litres  of  solution  passed  into  the  tree.  From  6 :00 
p.  m.  August  31  to  8:00  a.  m.  September  1  the  amount  taken  in  was 
1.4  litres;  from  8:00  a.  m.  to  3:00  p.  m.  September  1,  1.8  litres;  from 
3:00  p.  m.  September  1  to  8:00  a.  m.  September  2,  1.05  litres.  From 
this  time  the  amounts  absorbed  grew  smaller  until  work  with  the  tree 
was  discontinued  October  3. 

The  total  amount  of  solution  taken  in  by  the  tree  in  33  days  was 
18.33  litres.  The  first  injurious  effect  was  observed  on  the  morning 
of  September  4,  ninety  hours  after  the  attachment  was  made.  The 
tree  had  at  that  time  absorbed  9.6  litres  of  solution.  The  injury,  as 
first  seen,  consisted  in  a  discoloration  of  the  vascular  system  in  a  few 
of  the  lower  leaves  on  a  branch  directly  above  the  point  where  the 
solution  entered.  This  browning  was  visible,  at  first,  only  by  looking 
thru  the  leaves,  but  a  few  hours  later  it  had  spread  and  produced 
the  characteristic  surface  appearance.  The  morning  of  September 
5  these  leaves  were  completely  brown;  they  numbered  about  20.  No 
further  spread  of  this  injury  occurred.  September  13  some  of  the 
leaves  above,  on  the  same  branch  carrying  the  browned  leaves,  exhib- 
ited yellow  spots  which  gradually  enlarged  and,  on  the  morning  of 
September  14  several  leaves  were  entirely  yellow  and  ready  to  fall, 
and  were  removed.  Other  leaves  became  affected  in  the  same  way 
and  this  continued  until  every  leaf  on  the  branch  was  removed.  The 
two  branches  next  above  the  one  here  considered,  diverged  at  a  con- 
siderable angle  and  were  separated  vertically  by  several  inches.  A 


1909] 


BORDEAUX  MIXTURE 


241 


FIG.  2.     Tree  No.   14  supplied  with  solution  of  copper    sulphate    1:25000.  Yellowing 

of  leaves  was   produced   on   this   tree.     In   33    days   the  tree 

absorbed  18.33  litres  of  solution. 


242  BULLETIN  No.   135  [May 

few  inches  further  up  another  branch  projected  almost  immediately 
above  the  one  whose  leaves  had  fallen.  September  20  lower  leaves  of 
this  branch  showed  evidences  of  yellowing  and  the  next  day  several 
were  yellow.  Other  leaves  on  this  branch  became  affected  and,  by 
October  3  about  half  the  leaves  borne  by  this  branch  had  fallen.  No 
other  leaves,  besides  those  on  these  two  branches,  were  in  any  way 
affected,  nor  did  yellow  leaves  appear  on  other  trees  at  this  time.  It 
appears  that  the  yellowing  of  leaves  on  this  tree  was  caused  by  the 
copper  sulphate  solution  absorbed,  but  the  manner  in  which  the  injury 
was  produced  remains  for  future  investigation.  Of  the  leaves  that 
became  yellow,  97  were  collected  and  subjected  to  analysis.  They  con- 
tained 8.2  milligrams  of  copper  sulphate,  showing  quite  conclusively 
that  the  copper  penetrated  to  the  leaves.  The  results  obtained  from 
this  tree  and  from  others  in  the  series  indicate  possible  correlation  be- 
tween strength  of  solution  and  amount  of  copper  absorbed  on  the  one 
hand,  and  kind  and  degree  of  injury  on  the  other.  They  encourage 
continuance  of  this  line  of  investigation  which  was  stopped  by  the 
lateness  of  the  season. 

THE  RELATION  OF  METEORIC  WATERS  TO  FOLIAGE 

INJURY 

COVERED  AND  UNCOVERED  TREES 

The  opinion  has  been  frequently  expressed  that  injuries  to  leaves, 
following  the  applications  of  Bordeaux  mixture,  have  darect  relation  to 
atmospheric  conditions.  This  view  is  based  upon  the  observation  that 
brown  spotting,  more  or  less  severe,  often  follows  applications  made 
during  wet  weather,  or,  may  suddenly  appear  following  rain  that  is  de- 
fered  anywhere  from  one  to  six  weeks  or  longer.  Some  of  the  report- 
ed cases  of  injuries  that  appear  to  be  directly  connected  with  rainfall 
present  anomalies  not  readily  explained,  for  example,  trees  well  coated 
with  Bordeaux  mixture,  may  be  washed  by  rains  at  intervals  of  several 
days  and  no  injury  to  foliage  appears;  then  another  rain  falls,  and, 
immediately  after,  serious  injury  occurs.  A  case  in  point  happened  in 
our  station  work  in  an  orchard  in  the  western  part  of  the  state.  The 
fact  of  injury,  immediately  following  a  particular  rain,  naturally  sug- 
gests that  rain  as  the  immediate  cause,  but  why  did  not  earlier  rains 
have  the  same  effect?  Was  there  some  particular  quality  in  or  condi- 
tion attendant  on  this  rain  that  gave  it  a  power  for  injury  that  the 
other  rains  did  not  have?  These  are  questions  difficult  to  answer  be- 
cause of  incomplete  records.  The  injury  comes  unexpectedly.  It  is 
well  developed  when  discovered  and  the  restrospective  enumeration  of 
conditions  just  preceding  is  likely  to  miss  the  important  factor,  and 
thus  attach  an  element  of  uncertainty  to  any  conclusion  that  may  be 
reached.  Various  suggestions  have  been  offered  to  account  for  the 
injurious  action  of  some  rains,  as  contrasted  with  the  harmlessness  of 
others.  A  rain  is  injurious  because  the  waters  hold  in  solution  an  un- 
usual amount  of  carbon  dioxide  which  exerts  its  solvent  action  upon 


1909]  BORDEAUX  MIXTURE  243 

the  copper  compounds  on  the  leaves  and  this  copper  in  solution  effects 
the  injury.  An  electrical  condition  of  the  atmosphere  operates  upon 
the  copper,  and,  aided  by  the  water  brings  an  injurious  amount  into 
solution.  The  carbon  dioxide  of  the  air,  in  the  days  preceding  the 
rain,  converted  sufficient  copper  on  the  leaves  to  soluble  form  so  that 
only  moisture  was  needed  to  effect  the  injury.  These  and  other  like 
conjectures  have  no  tangible  basis ;  they  are  questions  difficult  to  prove 
for  particular  cases,  and  equally  difficult  to  disprove.  But  while  un- 
certainty may  attend  the  exact  manner  in  which  injuries  are  effected 
it  must  be  accepted  as  fact  that  meteoric  waters  do  play  an  important 
part.  Other  atmospheric  conditions,  temperature,  humidity,  electrical 
conditions,  wind,  clouds,  and  sunshine  may  one  or  all  have  influence  at 
times  and  contribute  to  the  effects  observed,  but  dew,  and  rain,  especial- 
ly the  latter,  must  be  regarded  as  the  most  active  agents  in  those  cases 
of  injury  that  occur  in  spite  of  all  precautions  taken  to  avoid  them. 
While  this  conclusion  is  based  upon  a  considerable  number  of  reports 
of  conditions  attending  particular  cases  of  injury  and  upon  many  field 
observations,  it  seemed  advisable  to  test  the  matter  in  a"  more  detailed 
manner.  To  this  end  two  four  year  old  apple  trees  growing  five  feet 
apart  in  rows  ten  feet  apart  were  selected  and  given  the  numbers  26 
and  27  in  the  regular  series  of  numbers  for  the  season  of  1906.  These 
trees  were  of  about  equal  size  and  form  as  indicated  by  the  following 
measurements : 

26  27 

Total  height  June  28 5  feet  5      inches        5  feet  2     inches 

Diameter  at  the  ground. ..  1^. inches  1^4  inches 

Ground  to  first  branches...  3  feet  3     inches        3  feet  2     inches 

Spread 2  feet  1  foot  9     inches 

During  the  season  tree  Number  26  added  1  foot  1  inch  to  its  height 
and  1  foot  8  inches  to  its  spread  while  tree  Number  27  increased  1  foot 
in  height  and  7  inches  in  spread.  The  trees  had  received  one  applica- 
tion of  Bordeaux  mixture  and  Paris  green  at  the  time  of  the  regular 
spraying  in  April,  but  at  the  commencement  of  this  test  no  traces  of 
the  early  application  could  be  found.  The  leaves  on  both  trees  were 
dark  green,  healthy  in  appearance  and  very  free  from  injuries  of  any 
kind.  On  the  morning  of  June  28  the  trees  were  sprayed  alike  with 
Bordeaux  mixture,  carefully  made,  after  the  4-4-50  formula.  Each 
tree  received  three  applications,  allowing  time  to  thoroly  dry  between 
applications.  When  dry  after  the  third  application  both  trees  pre- 
sented a  very  blue  appearance ;  the  leaves  were  thoroly  coated.  From 
this  time  until  October  13,  a  period  of  107  days,  tree  No.  26  was  ex- 
posed to  all  atmospheric  conditions,  while  tree  No.  27  was  protected 
from  dew  and  rain.  This  protection  was  secured  by  means  of  a  house- 
like  structure  so  adjusted  that  it  could  be  drawn  over  the  tree  at 
evening  or  at  any  time  when  rain  threatened.  The  cover  in  position 
and  the  uncovered  companion  tree,  at  the  left,  as  photographed  July 
4,  1906  are  shown  in  Figure  3. 

Full  exposure  was  allowed  every  day  except  when  there  was  im- 
mediate prospect  of  rain.  During  the  period  there  were  seven  full 


244 


BULLETIN  No.  135 


[May 


days  and  several  half  days  when  the  cover  remained  on  because  of 
rain.  No  rain  fell  on  the  remaining  days  of  June.  During  July  rain 
fell  on  11  days.  The  amounts  were  small  except  on  two  days — 0.6 
inch  July  12  and  0.55  inch  July  23.  The  total  for  the  month  was 
2.17  inches.  Both  trees  were  critically  examined  July  20  and  it  was 
then  plainly  evident  that  the  rain,  up  to  that  time  amounting  to  1.61 
inches,  together  with  the  possible  aid  of  the  frequent  heavy  dews, 
had  considerably  reduced  the  amount  of  Bordeaux  upon  the  leaves 
of  the  exposed  tree,  while  the  protected  tree  was  to  all  appearances 
as  well  coated  as  on  the  day  when  sprayed.  On  the  exposed  tree 
5  leaves  were  yellow  and  a  considerable  number  were  marked  by 


FIG.  3.     Two  trees  sprayed  alike  June  28.     The  one  on  the  left  exposed.     The  one 
on  the  right  protected  from  rain  and  dew  until  October  13,  a  period  of  107  days. 

brown  tips,  small  circular  spots  or  brown  marginal  areas.  These  in- 
juries individually  were  small  and,  as  the  majority  of  leaves  were 
uninjured,  the  entire  injury,  while  noticeable,  was  not  regarded  as 
serious.  On  the  protected  tree  no  leaves  were  injured. 

During  August  the  rainfall  was  nearly  twice  as  heavy  as  for 
July.  Rain  fell  on  12  days  giving  a  total  precipitation  of  4.2  inches. 
The  heaviest  rain  of  the  season  fell  during  the  night  of  August  17 
when  the  gauge  indicated  1.93  inches;  this  was  followed  by  showers 
on  August  18  and  19  bringing  the  precipitation  for  the  3  days  to  2.54 
inches.  This  heavy  rain  had  a  marked  effect  upon  the  exposed  tree 


1909]  BORDEAUX  MIXTURE  245 

in  removing  Bordeaux  from  the  leaves.  The  tree  lost  its  blue  color 
and  returned  to  normal  green  which  appeared  in  strong  contrast  with 
the  decided  blue  of  the  covered  tree.  The  yellow  leaves,  noted  as 
present  on  the  exposed  tree  on  July  20,  fell  during  rain  July  28,  and 
no  further  yellowing  occurred  until  August  11,  on  which  date  a  few 
were  noted.  A  few  days  later,  August  14,  a  few  leaves,  mainly  small 
basal  leaves  on  small  spurs  on  the  protected  tree  exhibited  the  lighter 
greenish  yellow  color  that  indicated  eventual  yellowing  and  death 
for  these  leaves.  On  the  unprotected  tree  there  was,  at  this  time,  an 
evident  increase  in  number  of  yellow  leaves.  August  17  the  yellow 
leaves  were  removed  by  hand  from  both  trees ;  there  were  55  from 
the  unprotected  tree  and  18  from  the  protected  tree.  On  the  unpro- 
tected tree  the  yellow  leaves  were  distributed  over  the  tree ;  many  of 
them  being  full  sized  leaves  on  terminal  shoots;  while  those  from 
the  protected  tree  were  almost  entirely  small  leaves  from  the  bases 
of  short  spurs.  The  number  of  leaves  removed,  cannot  be  taken  as 
representing  the  total  number  of  leaves  turning  yellow  on  the  two 
trees,  because  it  is  probable  that  some  fell  and  were  blown  away 
between  August  11,  when  yellowing  was  first  noticed,  and  the  date 
of  removal  of  those  remaining,  but  the  numbers  represent  very  well 
the  relative  yellowing  on  the  two  trees.  This  appearance  of  yellow 
leaves  on  these  two  trees  was  not  coincident  with  any  epidemic  of 
the  same  trouble  upon  other  trees  of  this  and  other  plats.  The  or- 
chards were  at  this  time  practically  free  from  yellow  leaves.  The 
cause  may  then  be  regarded  as  local  in  the  affected  trees  or  in  their 
treatment. 

About  the  middle  of  August  the  ravages  of  an  insect  pest  began 
to  show  conspicuously  on  the  leaves  of  the  unprotected  tree.  This 
insect,  the  apple  leaf  skeletonizer,  was  unusually  abundant  this  season. 
Attacking  the  leaves  as  it  does  in  late  summer,  after  the  protective 
influence  of  the  early  commercial  spray  has  been  largely  removed  by 
rains,  it  does  serious  injury,  particularly  to  young  trees.  The  coat- 
ing of  Bordeaux  mixture  present  on  the  leaves  of  the  tree  protected 
from  rain  was  sufficient,  altho  containing  no  arsenites,  to  ward  off 
attacks  of  this  insect  and  there  was  no  injury  except  on  a  few  of  the 
leaves  that  unfolded  after  the  spraying  was  done,  and  hence  had 
no  protective  covering.  The  unprotected  tree,  from  the  leaves  of 
which  the  Bordeaux  mixture  had  been  mostly  removed  by  rain,  had 
so  many  leaves  entirely  destroyed  and  so  many;  others  badly  injured 
that  the  general  appearance  of  the  tree  was  changed ;  the  foliage 
appeared  scant,  curled,  brown,  and  in  general,  unsightly.  This  served 
to  heighten  the  contrast  between  the  two  trees. 

Rain  to  the  amount  of  2.39  inches  fell  on  8  days  in  September 
and  there  was  one  light  rain  of  0.14  inch  in  October  before  the 
test  with  these  trees  was  discontinued. 

For  the  period  during  which  the  test  was  carried  on,  June  28 
to  October  13,  107  days,  the  total  rainfall  to  which  tree  No.  26 
was  exposed  and  from  which  tree  No.  27  was  protected  was  8.9 
inches.  As  already  remarked,  the  blue  color  imparted  to  the  leaves 


246  BULLETIN  No.   135  [May 

by  the  Bordeaux  mixture  disappeared  from  tree  No.  26  with  the 
rains  of  August  17-19,  but  some  leaves  retained  small  spots  of  the 
mixture  to  the  end.  These  spots  would  not  be  noticed  in  casual 
examination,  but  could  be  found  by  close  inspection  of  individual 
leaves.  The  foliage  of  tree  No.  27  kept  dry  during  this  period  of 
107  days  was  still  blue  October  13,  but  not  of  so  intense  a  blue  as 
had  existed  immediately  after  spraying.  It  is  probable  that  some 
of  the  Bordeaux  became  loosened  and  fell  as  dry  flakes  when  leaves 
were  rubbed  together  by  wind;  the  blue  color  was  also  toned  down 
by  accumulations  of  dust  which  settled  upon  the  leaves,  still  the  leaves 
were,  on  the  final  date,  October  13,  conspicuously  well  coated  and  blue 
in  color. 

All  leaves  on  both  trees  were  picked  October  13;  the  number 
from  tree  No.  26  was  1106,  from  tree  No.  27,  1506;  the  differ- 
ence of  400  between  the  two  trees  does  not  mean  that  tree  No.  27 
had  originally  a  greater  number  of  leaves  than  tree  No.  26,  but 
may  be  interpreted  as  showing  that  the  combined  action  of  the  skel- 
etonizer,  rain  and  wind  caused  the  fall  of  a  greater  number  of 
leaves  from  tree  No.  26  than  did  the  action  of  wind  alone  upon  tree 
No.  27. 

In  1907  this  test  was  repeated  on  the  same  trees  beginning  June 
10  and  ending  November  7,  making  the  period  150  days.  The  sea- 
son up  to  September  1,  covering  more  than  half  the  period  of  the 
test,  was  extremely  wet;  the  latter  part  of  the  period  was  rather 
dry  or  with  only  moderate  rains.  During  the  test  of  the  preceding 
year  the  exposed  tree  was  subjected  to  a  total  of  27  rains  and  there 
were  6  additional  days  on  which  there  were  traces  of  rain.  For 
1907  this  tree  was  exposed  to  46  rains  and  there  were  16  days  on 
which  there  were  traces  of  rain.  The  precipitation  for  the  period 
was  14.88  inches  and  more  than  three-fourths  of  this  fell  before 
September  1.  The  trees  as  they  appeared  October  17,  1907,  are 
shown  in  figure  4. 

One  notable  difference  between  the  two  tests  was  the  greater 
adhesiveness  of  the  Bordeaux  on  the  exposed  tree  in  1907  as  com- 
pared with  1906.  The  heavy  rains  of  July  and  August,  1907,  reduced 
the  blue  color  of  the  leaves  somewhat,  but  on  Sepember  1  trunk  and 
branches  were  still  very  blue ;  some  leaves  had  a  full  coating  and 
nearly  all  other  leaves  bore  conspicuous  blue  patches.  Later  rains 
did  not  greatly  reduce  the  amount  adhering  and,  when  the  leaves 
were  gathered  November  7,  a  large  proportion  of  them  still  retained 
considerable  Bordeaux  mixture.  It  is  not  thought  probable  that  the 
difference  in  adhesiveness  can  be  ascribed  to  differences  in  the  rains 
to  which  the  tree  was  subjected,  but  is  more  likely  due  to  differences 
in  the  lime  used  in  making  the  mixture.  There  is  no  definite  data 
on  this  -point  at  hand,  but  in  other  experiments  it  has  been  found 
that  character  of  the  lime  has  a  marked  influence  on  adhesiveness 
and  that  two  lots  of  the  same  brand,  both  equally  fresh  and  not  at 
all  air-slaked,  may  give  mixtures  that  are  unequal  in  a  marked  de- 
gree in  the  matter  of  adhesiveness. 


1909] 


BORDEAUX  MIXTURE 


247 


Leaves  of  the  covered  tree  remained  free  from  injury  thru- 
out  the  season  and  except  for  the  dullness  of  color  due  to  accumu- 
lated dust  were  as  blue  when  picked  as  in  the  first  days  following 
the  applications  June  10.  No  yellowing  of  leaves  appeared  on  either 
tree,  but  leaves  of  the  exposed  tree  were  marked  by  brown  spots  and 
marginal  areas  to  about  the  same  extent  as  were  those  from  the  same 


FIG.  4.     Two  trees  sprayed  alike  June  10,  1907.     The  tree  on  the  left  exposed.     The 
tree  on  the   right  protected  from  rain  and  dew  until  November  7,  a  period  of  150  days. 

tree  in  the  preceding  year.  Again,  for  the  third  time  this  test  was 
repeated  in  1908.  This  time  on  two  trees  in  another  plat,  and  under 
abnormally  dry  conditions.  The  precipitation  for  the  full  period  of 
the  test  was  6.36  inches,  less  than  half  the  amount  for  the  preced- 
ing year.  Results,  as  far  as  action  on  foliage  is  concerned,  were 
essentially  the  same  as  for  the  other  trials. 


248  BULLETIN  No.   135  [May 

The  uniformity  of  the  results  obtained  under  the  widely  differ- 
ent conditions  which  characterized  the  three  seasons,  fully  establish 
the  importance  of  meteoric  waters  in  their  relation  to  injury  to  foliage 
following  applications  of  Bordeaux  mixture.  In  no  case  was  there 
any  appearance  of  injury  on  leaves  of  the  protected  trees,  while  in 
each  test  the  foliage  of  the  tree  exposed  to  rain  was  in  some  de- 
gree injured.  The  utmost  care  was  taken  in  the  preparation  of  the 
mixtures,  applications  were  the  same  for  the  trees  compared  and 
all  conditions  were  equal  except  in  the  one  matter,  that  in  each  test 
one  tree  was  protected  from  rain  and  dew.  Injuries  to  foliage  of 
the  exposed  trees  were  not  very  serious,  and  yet,  an  aggregate  of  the 
dead  leaf  areas  must  have  reduced  the  working  leaf  surface  to  an 
appreciable  and  undesirable  extent.  By  no  means  all  leaves  were 
affected ;  often  of  two  contiguous  leaves,  one  would  be  perfectly  healthy 
while  its  neighbor  was  clead  at  the  tip  or  had  long  narrow  strips  of  dead 
tissue  along  the  margin  or  was  more  or  less  disfigured  by  circular  or 
irregular  brown  areas  of  varying  size,  distributed  over  the  surface. 
Why  one  of  two  neighboring  leaves,  apparently  exactly  alike  and 
having  the  same  exposure,  should  be  injured  and  the  other  not  affected 
is  an  unanswered  question.  A  suggested  inequality  in  composition 
and  distribution  of  the  mixture  is  not  an  acceptable  explanation,  be- 
cause agitation  before  and  during  the  process  of  spraying  was  so 
thoro  that  composition  must  have  been  uniform.  It  is  certainly  not 
a  question  of  quantity,  because  of  two  leaves  the  injured  may  show 
a  decidedly  less  amount  of  Bordeaux  upon  its  surface  than  the  un- 
injured. Slight  structural  differences,  or  varying  degrees  of  vitality 
might  be  assumed  to  account  for  differences  in  liability  to  injury  but 
there  is  no  proof  of  the  existence  of  such  differences  and  the  question 
remains  open  for  further  investigation. 

CHANGES  OCCURRING  IN  BORDEAUX  MIXTURE 

If  attention  is  given  to  the  selection  of  materials,  and  if  these  ma- 
terials are  brought  together  in  proper  proportions  in  accordance  with 
standard  formulas,  no  copper  remains  in  the  clear  supernatant  liquid, 
as  the  precipitate  subsides.  In  this  fact  we  have  evidence  that  the 
copper  has  all  been  converted  into  insoluble  compounds  and  the  Bor- 
deaux mixture  rendered  safe  for  application  to  foliage.  If  the  mix- 
ture is  allowed  to  stand,  changes  take  place.  These  changes  may 
occur  more  or  less  promptly,  according  to  the  quality  and  quantity 
of  lime  present  and  are  first  apparent  in  the  color  of -the  mixture. 
The  bright  sky  blue  characteristic  of  well  made  Bordeaux  becomes 
darker,  greenish  shades  appear  and  finally  the  precipitate  assumes 
and  retains  a  dingy  purple  color.  The  chemical  transpositions  that 
occur  have  not  been  determined,  but  it  is  known  that  some  of  the 
copper  becomes  soluble  and  that  for  this  reason  mixtures  that  have 
stood  for  some  time  are  not  safe  to  apply.  Color  appears  to  be  a 
guide  that  can  be  depended  upon.  As  long  as  the  original  blue  is 
retained  there  appears  to  be  no  difference  in  the  effect  upon  foliage 
between  perfectly  fresh  mixture  and  that  which  has  stood  for  a 


1909]  BORDEAUX  MIXTURE  249 

week  or  more.  However,  it  is  the  common  practice  to  use  only  fresh 
made  mixtures,  both  because  they  are  safer  and  usually  most  con- 
venient. 

If  changes  occur  in  Bordeaux  mixture  in  mass,  it  is  reasonable 
to  believe  that  similar  or  possibly  much  more  radical  changes  will 
occur  when  the  mixture  is  sprayed  upon  foliage  and  thus  spread  out 
with  maximum  exposure  to  the  air  and  the  elements.  The  color 
changes  frequently  observed  in  mixtures  in  bulk  do  not  usually  ap- 
pear in  mixtures  thinly  spread  on  foliage;  the  original  blue  is  re- 
tained thruout  the  season  or  as  long  as  the  coating  remains  on  the 
leaves.  Sometimes  burning  of  the  leaves  follows  immediately  upon 
application,  in  other  cases  like  injury  may  appear  after  a  delay  of 
several  days  or  even  several  weeks;  degree  of  injury  may  vary  from 
slight  to  the  nearly  complete  defoliation  of  the  trees;  and  again  no 
injury  that  can  in  any  way  be  connected  with  the  mixture  occurs, 
the  leaves  remain  in  perfectly  healthy  condition  and  perform  their 
functions  to  the  normal  end  of  the  season. 

THE  PROBLEM  OF  SOLUBILITY  OF  THE  COPPER  OF 
BORDEAUX  MIXTURE  ON  LEAVES 

Early  in  this  investigation  of  injuries  to  foliage  by  materials 
applied  in  spraying,  repeated  tests  were  made  of  the  separate  in- 
gredients of  Bordeaux  mixture.  Trees  were  sprayed  heavily  with 
milk  of  lime  of  varying  degrees  of  concentration  and  to  other  trees 
solutions  of  copper  sulphate  in  varying  degrees  of  dilution  were  ap- 
plied. In  no  case1  was  any  injury  inflicted  by  milk  of  lime,  but  it 
was  clearly  demonstrated  that  injury  promptly  followed  the  applica- 
tion of  even  very  dilute  solutions  of  copper  sulphate.  These  injuries 
are  of  the  same  character  as  those  that  follow  spraying  with  Bor- 
deaux mixture.  It  is  therefore  concluded  that  the  copper  in  solution 
is  the  active  agent  responsible  for  the  burning  of  foliage.  Numerous 
tests  show  that  fresh  and  rightly  made  Bordeaux  mixture  contains 
no  soluble  copper.  We  must  then  conclude  that  changes  take  place 
in  Bordeaux  mixture  after  deposition  on  the  leaves,  and  that  copper 
becomes  soluble,  at  least  in  some  cases,  in  sufficient  quantity  to  erfect 
injury.  Numerous  observations  made  in  the  field,  and  critical 
study  of  particular  cases  of  injury,  have  suggested  several  ques- 
tions, answers  to  which  are  necessary  to  an  understanding  of  the 
anomalous  and  often  contradictory  results  following  field  experi- 
ments in  the  application  of  Bordeaux  mixtures.  How  soon  after 
deposition  on  the  leaves  does  soluble  copper  appear?  Thru  what 
agencies  does  copper  become  soluble?  Does  absence  of  injury  mean 
absence  of  copper  in  solution?  Is  appearance  of  injury  synchronous 
with  appearance  of  soluble  copper?  Does  the  presence  of  lime  in 
excess  prevent  or  retard  solubility  of  copper?  Is  the  view  expressed 
by  Millardet  and  Gayon,  that  copper  remains  in  insoluble  form  until 
all  free  lime  has  been  neutralized  or  washed  away,  correct?  With 
what  degree  of  rapidity  is  excess  lime  removed?  Does  the  appear- 
ance of  injury  correlate  with  entire  removal  of  free  lime?  A  con- 


250  BULLETIN  No.   135  [May 

siderable  number  of  experiments  have  been  conducted  for  the  pur- 
pose of  finding  answers  to  these  and  other  questions  of  like  nature, 
and  we  may  now  consider  a  portion  of  these  experiments  in  some 
detail. 

It  is  a  currently  expressed  opinion  that  the  insoluble  copper 
compounds  deposited  on  the  leaves  in  Bordeaux  mixtures  are  acted 
upon  by  the  carbon  dioxide  of  the  air  and  by  the  carbon  dioxide, 
ammonia,  and  nitric  acid  contained  in  dew  and  rain  waters  and  thru 
these  agencies  converted  into  soluble  forms  which  are  then  capable 
of  working  injury  to  the  leaves. 

BORDEAUX  MIXTURE  IN  GLASS  DISHES 

Following,  in  part,  a  test  reported  by  Schander1  20  c.c.  of  Bor- 
deaux mixture  carefully  made  on  the  4 — 1—50  formula  and  which  con- 
tained no  copper  in  solution  was  placed  in  each  of  4  six  inch  crystal- 
lizing dishes  on  May  12.  The  dishes  were  given  the  numbers  16, 
17,  18  and  19.  Nos.  16  and  17  were  placed  in  shade  on  a  labora- 
tory table,  Nos.  18  and  19  in  a  south  window  as  much  exposed  to 
the  sun  as  possible.  No.  17  in  shade  and  No.  19  in  sun  were  kept 
permanently  dry.  No.  16  in  shade  and  No.  18  in  sun  were  moistened 
with  cistern  water  almost  daily,  or  to  be  exact,  54  times  in  the  65  days 
to  and  including  July  16.  July  16,  the  dishes  were  placed  in  the 
hands  of  the  chemists  for  examination  of  the  contents  and  determin- 
ation of  the  state  of  the  copper  as  regards  solubility.  Below  is  the 
report  submitted,  with  conclusions,  by  Dr.  H.  S.  Grindley  and  Mr. 
O.  S.  Watkins. 

BORDEAUX  MIXTURES.    REPORT  UPON  NUMBERS  16-19,  INCLUSIVE 
Received  July  16,  1906 

Each  of  the  residues  in  the  crystallizing  dishes  was  digested 
thoroly  with  cold  neutral  distilled  water.  The  filtrates  were  very 
slightly  alkaline  to  litmus  paper  but  they  were  very  slightly  acid  to 
phenolphthalein. 

To  make  the  filtrates  neutral  to  phenolphthalein  it  took  the  fol- 
lowing amounts  of  lV/2o  NaOH  solution — No.  16,  0.35  c.c. ;  No.  17, 
0.31  c.c.;  No.  18,  0.40  c.c.;  No.  19,  0.40  c.c. 

The  solutions  before  titration  and  after  titration  were  perfectly 
colorless  and  therefore  did  not  show  any  indication  of  copper. 

The  neutralized  solutions  were  evaporated  to  a  very  small 
volume  (5-10  c.c.).  They  were  slightly  acidified  with  a  few  drops 
of  H2SO4  and  then  treated  with  hydrogen  sulphide  gas.  No  trace 
of  a  precipitate  of  copper  sulphide  appeared.  Not  even  a  dark  color- 
ation of  the  solution  was  produced.  These  filtrates  were  saved  under 
the  labels  16A,  17A,  ISA,  and  19A. 

The  residues  remaining  from  the  extracts  with  cold  water  were 
distinctly  blue  in  color  and  they  apparently  consisted  largely  of  in- 
soluble copper  salts.  They  were  treated  with  a  few  c.c.  of  diluted 
nitric  acid.  They  effervesced  vigorously,  showing  much  carbonic  acid. 

iSchander,   R.      Landw.   Jahrb.   33    (1904),   p.   522. 


1909]  BORDEAUX  MIXTURE  251 

The  residues  readily  and  completely  dissolved  in  the  dilute  nitric  acid. 
The  solutions  thus  resulting  were  saved  with  the  labels  Nos.  16B, 
17B,  18B,  and  19B. 

Conclusions. — First  by  the  action  of  the  air. or  by  the  air  and 
water  used  in  moistening  the  Bordeaux  mixtures  no  soluble  copper 
salts  were  produced.  At  least  after  the  action  had  continued  from 
the  12th  day  of  May  to  the  present  time,  there  was  no  soluble  copper 
salts  in  either  of  the  four  cases. 

Second,  the  strong  akalinity  due  to  the  lime  of  the  Bordeaux 
mixture  had  been  completely  neutralized  by  the  action  of  the  air 
and  moisture.  The  lime  and  the  copper  had  apparently  been  mostly 
converted  into  the  carbonates  of  those  metals. 

Signed        H.  S.  GRINDLEY, 
July  20,  1906.  O.  S.  WATKINS. 

BORDEAUX  MIXTURE  ON  FOLIAGE  OF  APPLE  TREES  IN  POTS 

In  order  to  more  nearly  approximate  the  actual  conditions  to 
which  Bordeaux  mixture,  as  sprayed  on  foliage,  is  subjected,  a  fur- 
ther test  of  exposure  to  atmospheric  conditions  in  a  constantly  dry 
condition  and  in  an  intermittently  wet  condition  was  made  as  follows : 

Two  one  year  old  Northwestern  Greening  apple  trees,  growing 
in  eight-inch  pots,  were  sprayed  at  the  same  time  and  with  the  same 
Bordeaux  mixture,  freshly  made  after  the  4-4—50  formula.  The 
trees  were  sprayed  three  times,  allowing  intervals  sufficient  to  thoroly 
dry  the  foliage  between  applications.  When  finally  dried  both  trees 
were  thoroly  coated.  The  spraying  was  done  on  May  24,  and  the 
trees,  to  which  the  numbers  81  and  83  had  been  given  were  then 
placed  side  by  side,  on  the  sill  of  a  south  window.  No.  83  was  kept 
continually  dry.  No.  81  was  sprayed  with  cistern  water  (delivered 
in  a  fine  mist  by  means  of  an  atomizer)  on  46  of  the  54  days  of  the 
period  from  May  24  to  July  17.  In  these  applications  of  water,  the 
amo'unt  was  regulated  to  simply  moisten  the  Bordeaux  upon  the  leaves, 
without  causing  any  removal  of  material  by  dripping.  July  17  the 
the  trees  were  given  to  the  chemists  and  report  of  the  examination  for 
soluble  copper  is  given  herewith : 

REPORT  ON  FOLIAGE  INJURY  WORK.     Nos.  20  AND  21 
Received  July  17,  1906 

The  leaves  and  small  stems  of  tree  No.  81  were  washed  as  free  as 
possible  from  the  Bordeaux  mixture  with  neutral  distilled  water.  After 
drying,  the  leaves  of  the  tree  showed  a  white  residue  still  remaining 
(probably  a  mixture  of  CaCO3  and  CaSOJ,  but  scarcely  any  of  the 
blue  residue  of  the  copper  salt. 

The  residue  washed  off  the  leaves  with  the  water  was  removed 
from  the  latter  by  filtration  which  gave  a  clear,  colorless  filtrate  and  a 
green  colored  residue.  The  residue  was  dissolved  in  dilute  nitric 
acid  and  saved  under  the  label  No.  81b.  The  treatment  with  acid 
caused  the  evolution  of  CO2  in  considerable  quantity. 


252  BULLETIN  No.   135  [May 

The  filtrate  was  very  slightly  alkaline  to  litmus,  but  very  slightly 
acid  to  phenolphthalein.  It  required  0.75  c.c.  N/10  KOH  to  make  the 
solution  neutral  to  phenolphthalein. 

The  solution  was  labelled  8 la,  evaporated  to  a  small  volume  and 
tested  for  soluble  copper  compounds  by  treating  with  hydrogen  sul- 
phide. An  excess  of  hydrogen  sulphide  gave  no  precipitate.  The  so- 
lution was  not  even  darkened  by  the  H2S.  This  proves  that  no  soluble 
copper  salts  were  present. 

The  leaves  and  small  stems  of  tree  No.  83  were  washed  with  neu- 
tral distilled  water  as  well  as  possible.  After  drying,  the  leaves  showed 
practically  the  same  coating  as  described  above  for  tree  No.  81. 

The  residue  washed  off  the  leaves  was  separated  and  treated  as 
described  above  in  the  case  of  tree  No.  81.  The  residue  insoluble  in 
water  was  dissolved  in  dilute  nitric  acid  and  saved  under  the  label 
No.  83b.  The  addition  of  the  nitric  acid  caused  considerable  CO2  to 
be  evolved. 

The  filtrate  was  very  slightly  alkaline  to  litmus,  but  very  slightly 
acid  to  phenolphthalein.  It  required  0.75  c.c.  N/10  KOH  to  make  the 
solution  neutral  to  phenolphthalein.  The  solution  was  labeled  83a 
evaporated  to  a  small  volume  and  tested  for  soluble  copper  compounds 
by  treating  it  with  hydrogen  sulphide.  The  excess  of  hydrogen  sulphide 
gave  no  precipitate.  The  solution  was  not  even  darkened  by  the  H2S. 
This  proves  that  no  soluble  copper  salts  were  present. 

CONCLUSIONS 

First,  by  washing  the  leaves  of  these  trees  with  neutral  distilled 
water  no  unchanged  lime  or  calcium  hydroxide  was  removed  by  the 
process.  That  is,  apparently,  the  alkalinity  of  the  original  Bordeaux 
mixture  due  to  the  excess  of  lime  used  in  making  it,  was  either  neu- 
tralized by  the  CO2  of  the  air,  or  by  the  acid  constituents  upon  the  sur- 
face of  the  leaves,  or  the  lime  was  washed  out  by  the  water  if  the  latter 
was  used  in  sufficient  quantity  to  run  or  drip  off  the  leaves. 

Second,  by  washing  the  leaves  of  these  trees  with  neutral  distilled 
water  no  soluble  copper  salts  were  removed. 

Third,  the  insoluble  greenish-blue  residue  washed  from  the  leaves 
dissolved  readily  in  dilute  nitric  acid  and  it  contained  considerable 
carbon  dioxide  in  the  form  of  a  carbonate.  By  the  washing  consid- 
erable quantities  of  insoluble  copper  compounds  were  removed  from 
the  leaves. 

Fourth,  no  differences  in  any  respects  could  be  observed  between 
the  solutions  or  the  insoluble  residues  washed  off  from  the  two  trees. 

July24,  1906.  Signed    H-  S-  GRINDLEY. 

The  results  of  these  two  experiments  exactly  coincide.  In  neither 
case  was  copper  in  solution  detected.  The  Bordeaux  remaining  in 
glass  dishes  for  65  days  in  full  exposure  to  the  air,  and  whether  kept 
dry  or  intermittently  wet,  did  not  have  any  of  its  copper  converted  to 
soluble  form,  but  did  have  all  of  its  excess  calcium  oxide  rendered 
inert.  Likewise,  in  the  case  of  the  sprayed  trees,  no  copper  became 


1909]  BORDEAUX  MIXTURE  253- 

soluble,  but  the  lime  was  all  changed  to  insoluble  form.  It  should  be 
stated  in  regard  to  the  trees  that  all  leaves  were  thoroly  coated 
with  the  Bordeaux  mixture,  that  there  was  no  apparent  diminution 
of  the  blue  color  and  that  no  burning  or  brown-spotting  occurred. 

FIELD  EXPERIMENTS  WITH  SPRAYED  TREES  IN  1906. 

While  these  experiments,  which  were  carried  on  in  the  laboratory, 
were  in  progress,  plans  were  made  for  certain  other  field  experiments 
designed  to  supplement  the  laboratory  series  and  to  answer  some 
questions  which  those  experiments  were  not  calculated  to  reach.  In- 
formation was  particularly  desired  regarding  the  conditions  under 
which  and  the  time  when  soluble  copper  first  appeared,  the  rapidity 
with  which  it  became  soluble  and  the  relation  between  the  appearance 
of  copper  and  injuries  to  leaves.  It  was  also  deemed  important  that 
an  attempt  be  made  to  correlate  weather  conditions  and  any  changes 
that  took  place  in  the  Bordeaux  spread  upon  the  leaves.  It  was, 
therefore,  arranged  to  equip  certain  four  year  old  apple  trees,  growing 
in  the  department  plats,  with  appliances  for  catching  and  holding  rain 
or  spray  waters  passing  over  the  leaves  and  then  subjecting  the  waters 
collected  to  chemical  analysis,  for  determination  of  alkalinity,  soluble 
copper  and  arsenic.  The  trees  chosen  were  those  that,  from  location, 
size  and  form  of  crown,  seemed  best  adapted  for  the  purpose. 

Each  tree  was  supplied  with  a  ring  made  of  quarter  inch,  round, 
galvanized  iron,  forty  inches  in  diameter.  This  ring  was  supported, 
above  the  greatest  spread  of  the  tree,  at  a  height  between  five  and  six 
feet,  by  four  wooden  posts,  so  braced  as  to  prevent  any  displacement 
by  wind.  From  this  ring  a  funnel,  made  of  a  heavy  grade  of  table  oil- 
cloth, was  suspended  and  so  adjusted  about  the  trunk  of  the  tree  that 
no  water  could  escape  except  thru  the  mouth  of  the  funnel,  which 
was  arranged  to  open  into  a  five  gallon  jar  supported  in  proper  posi- 
tion. The  arrangement  as  described  was  then  surrounded  with  a  bur- 
lap curtain,  to  prevent  rain  from  driving  against  the  outside  of  the 
funnel  and  dripping  into  the  jar. 

Five  trees,  designated  by  the  numbers  33,  34,  35  and  36  and  49 
were  thus  equipped  during  the  summer  of  1906. 

TREE  NUMBER  33 

The  preliminary  spray  was  applied  to  tree  No.  33  July  21.  For 
this  spray  the  mixture  in  most  common  use  in  the  commercial  orchards 
of  the  state  was  used.  The  formula  is  as  follows : 

Copper   sulphate 4      pounds 

Fresh  slaked  lime 4      pounds 

Paris  green l/$  pound 

Water 50      gallons 

The  tree  was  sprayed  three  times  allowing  intervals  sufficient  for 
thoro  drying  between  applications.  When  spraying  was  completed, 
the  tree  was  thoroly  coated.  The  funnel  was  then  adjusted  and  the 
tree  left  exposed  to  the  sun  and  to  any  rains  that  might  fall.  July  28, 
seven  days  after  spraying,  the  first  rain  came  as  a  thunder  shower  with 


254  BULLETIN  No.   135  [May 

precipitation  amounting  to  0.55  inch.  The  water  falling  within  the 
ring,  most  of  which  passed  over  the  sprayed  leaves  to  the  jar  below, 
measured  11.28  litres  (approximately  three  gallons).  This  water  was 
taken  to  the  chemical  laboratory,  filtered,  a  sample  taken  for  determin- 
ation of  alkalinity,  the  balance  concentrated  by  evaporation  and  stored 
for  subsequent  determination  of  copper  and  arsenic.  The  residue, 
left  on  filtering,  and  which  was  seen  to  contain  many  small  flakes  and 
particles  of  insoluble  Bordeaux,  was  also  preserved  for  determination 
of  the  insoluble  copper.  Other  rains  followed  at  intervals  of  from 
one  to  nine  days  until  October  13,  on  which  date  the  leaves  remaining 
were  picked  and  work  with  the  tree  discontinued.  During  the  period 
of  84  days  from  July  21  to  October  13  the  tree  was  subjected  to  the 
waters  of  twenty-one  rains,  varying  in  amount  from  0.01  inch  to  1.93 
inches,  and  which  classify  as — thunder  storms  7;  light  local  showers 
11 ;  protracted  rains  3.  The  total  precipitation  was  7.30  inches.  The 
21  lots  of  water  collected  ranged  from  304  c.c.  to  20,191  c.c. ;  from 
less  than  one  pint  to  more  than  five  gallons.  The  aggregate  was  a  lit- 
tle more  than  33  gallons.  To  this  should  be  added  about  five  gallons, 
making  the  total  water  falling  within  the  ring  approximately  38  gal- 
lons. This  addition  is  explained  by  the  fact  that  the  heaviest  rain 
(1.93  inches  August  17)  came  during  the  night,  and  the  amount  fall- 
ing within  the  ring  exceeded  the  capacity  of  the  jar,  so  that  a  quantity, 
computed  from  the  ratios  of  other  rains  at  about  five  gallons  was  lost. 

The  spray  applied  to  this  tree  was  much  in  excess  of  applications 
made  in  common  orchard  practice;  kaves  and  branches  were  thoroly 
coated  and  were  uniformly  of  a  Bordeaux  blue  color.  Notwithstand- 
ing the  heavy  application,  injury  to  foliage  was  extremely  small.  Two 
days  after  the  rain  of  July  28,  that  is  to  say,  nine  days  after  spraying, 
a  very  slight  browning  on  the  margins  of  a  few  leaves  was  observed. 
This  injury  was  neither  conspicuous,  nor  in  any  way  serious.  Two 
weeks  later,  immediately  following  the  showers  of  August  10  a  few 
small  brown  spots  were  noted  on  a  few  of  the  leaves.  During  the  sea- 
son a  few  leaves  became  yellow  and  fell ;  these  were  mainly  the  small 
basal  leaves  of  clusters.  This  yellowing  can  not  be  ascribed  to  any 
effect  of  the  spray  for  the  reason  that,  at  the  same  time,  a  somewhat 
larger  number  of  yellow  leaves  was  observed  on  similar  trees  that  had 
not  been  sprayed.  On  completion  of  the  chemical  analyses  the  results 
were  brought  together  as  shown  in  the  tabulation  page  255. 

The  significant  feature  of  the  results,  as  tabulated,  is  the  early  and 
continuous  appearance  of  soluble  copper.  An  appreciable  quantity — 
16.5  milligrams  per  litre — was  present  in  the  waters  from  the  rain 
which  fell  seven  days  after  spraying.  With  the  exception  of  the  sec- 
ond rain,  the  amount  of  water  from  which  was  very  small,  measure- 
able  amounts  of  copper  were  determined  from  the  waters  of  all  follow- 
ing rains.  The  amount  varied  between  8.9  milligrams  and  85  milli- 
grams per  litre.  There  is  marked  irregularity  in  the  amounts  of  cop- 
per indicated  and  no  definite  relation  can  be  traced  between  these 
amounts  and,  either  intervals  of  time,  or  character  of  the  storms.  In 
some  cases  it  appears  that  small  amounts  of  drip  waters  give  propor- 


1909] 


BORDEAUX  MIXTURE 


255 


tionately  larger  quantities  of  copper  than  do  the  larger  amounts,  but 
this  does  not  hold  for  all  cases.  No  satisfactory  reason  has  been  found 
to  account  for  such  fluctuations  as  appear  between  waters  from  the 
rains  of  September  19  to  September  27.  After  a  time  interval  of  7 
days  a  local  shower  with  precipitation  of  0.09  inch  giving  1.7  litres  of 
drip,  yields  copper  to  the  amount  of  56.1  milligrams  per  litre ;  then  fol- 
lowing an  internal  of  3%  days  another  local  shower  of  0.43  inch  and  9 
litres  of  drip  gives  22.2  milligrams  per  litre ;  next,  after  the  same  in- 
terval a  light  shower  measuring  0.03  of  an  inch  and  giving  0.9  litre  of 
water  shows  84.9  milligrams  of  soluble  copper  per  litre,  and  following 


Chemical  Determinations  from  Waters  Collected  from  Tree  Number  33. 


Soluble  constituents  of  drip  waters 

Sediment  filtered  from  drip  waters 

Serial 

Date 

Amount 
of 

J    *_ 

Copper 

Alkalinity   in   terms 
of  calcium  oxide 

Arsenic  in 

Insoluble  copper 

Insoluble  arsenic 

Number 

drip 

Total 

Milligrams 

Total 

Millierams 

terms  of 
As203 

Total 

Milligrams 

Total 

Milligrams 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

33 

July       29 

12.23 

202.0 

16.5 

105.8 

8.6 

1.5 

773.6 

6.3 

121.5 

9.9 

33  b 

July       30 

.31 

Trace 

Trace 

None 

Trace 

Trace 

33  c 

August    5 

2.32 

-    87.2 

37.5 

10.5 

4^5 

Trace 

301.6 

13.0 

24.1 

10^3 

33  e 

August    7 

1.25 

42.4 

33.9 

4.1 

3.2 

Trace 

103.6 

82.8 

20.1 

16.0 

33  f 

August    8 

5.73 

57.2 

9.9 

33.7 

5.8 

Trace 

390.4 

68.1 

33.4 

5.8 

33  g 

August    9 

1.40 

19.6 

14.0 

5.8 

4.1 

Trace 

349.2 

249.4 

20.6 

14.4 

33  h 

August  10 

7.18 

64.0 

8.9 

47.1 

6.5 

1.0 

398.8 

55.5 

39.0 

5.4 

33  i 

August  18 

20.90 

696.0 

33.3 

87.2 

4.1 

2.0 

291.2 

13.9 

12.6 

0.6 

33  j 

August  18 

3.55 

32.4 

9.1 

18.3 

5.1 

Trace 

174.8 

49.2    |      10.4 

2.9 

33  k 

August  19 

8.67 

94.4 

10.8 

26.5 

3.0 

Trace 

389.6 

45.1 

19.7 

2.2 

331 

August  24 

1.50 

22.8 

15.2 

1.3 

0.8 

Trace 

104.4 

69.6 

Trace 

33  n 

August  26 

14.80 

154.0 

10.4 

14.5 

0.9 

Trace 

337.2 

22.7 

27.4 

1^8 

33  o 

Sept.        3 

1.25 

15.2 

12.1 

Too  dark 

0.90 

70.4 

56.3 

10.5 

8.4 

33  p 

Sept.      12 

1.77 

75.6 

42.7 

Too  dark 

0.50 

61.6 

34.8 

Trace 

33  q 

Sept.      19 

1.70 

95.4 

56.1 

Too  dark 

Trace 

300.8 

176.9 

13.7 

8.0 

33  r 

Sept.      22 

9.00 

200.0 

22.2 

Neutral 

0.70 

348.8 

38.7   !     24.2 

2.7 

33s 

Sect.      26 

0.90 

76.4 

84.9 

Too  dark 

Trace 

40.4 

44.9       Trace 

33  t    i  Sept.      27 

5.72 

80.0 

13.9 

Too  dark 

Trace 

130.8 

22.8         10.7 

1.8 

33  u 

Sept.      29 

10.51 

204.4 

19.4 

Neutral 

0.8 

275.6 

26.2 

19.8 

1.8 

33  v 

October  1 

17.26 

207.2 

11.8 

Neutral 

1.0 

217.2 

12.6 

21.4 

1.2 

33  w 

October  4 

2.28 

72.4 

31.7 

Too  dark 

Trace 

121.6 

53.3 

9.7 

4.2 

this  in  12  hours  another  shower  precipitating  0.27  inch  and  yielding 
5.72  litres  of  water  gives  13.9  milligrams  of  copper  per  litre. 

Alkalinity  decreases  until  neutrality  is  reached  about  the  first  of 
September,  but  the  rate  of  decrease  is  not  uniform.  The  solid  resid- 
ues, remaining  after  filtering,  yield  appreciable  amounts  of  insoluble 
copper  thruout  the  season.  But,  as  with  the  soluble  copper,  the  quan- 
tities showed  marked  fluctuations. 

As  regards  arsenic,  only  very  minute  amounts  become  soluble  but 
its  appearance  continues  to  the  end.  Most  of  the  arsenic  is  recovered 
from  the  insoluble  residues  and  it  is  interesting  to  note  that  the  Bor- 
deaux holds  the  Paris  green  tenaciously.  Some  particles  were  carried 
down  by  every  rain  that  fell,  even  to  the  last  on  October  4,  but  in  no 
case  was  the  amount  large. 


256 


BULLETIN  No.   135 


[May 


TREE  NUMBER  34 

The  equipment  for  tree  No.  34  was  similar  to  that  provided  for 
No.  33,  but  with  this  addition :  a  waterproof  cover  was  supplied  which 
was  adjusted  over  the  tree  every  evening  and  whenever  there  was 
immediate  prospect  of  rain  during  the  day,  so  that  meteoric  waters 
were  effectually  excluded.  The  tree  was  sprayed  July  24  in  a  manner 
exactly  like  tree  33  and  with  a  mixture  made  on  the"  same  formula. 
When  the  spraying  was  completed  the  coating  was  as  complete  and  the 
color  of  the  leaves  as  blue  as  was  tree  33.  The  funnel  was  then  ad- 
justed and  the  cover  placed  ready  for  use.  The  plan  for  this  tree 
was,  to  substitute  for  natural  rain,  an  artificial  spray  of  cistern  water 
applied  at  definite  intervals  of  one  week  until  four  applications  had 
been  made.  To  this  end  an  application  was  made  July  31.  The  spray 
was  directed  upon  the  leaves  thru  a  single  Vermorel  nozzle  applied 
at  a  pressure  of  about  100  pounds  from  a  barrel  pump  operated  by 
hand,  and  in  a  manner  to  wash  the  leaves  as  thoroly  as  possible.  The 
spraying  continued  for  six  minutes,  and,  after  drip  from  the  leaves 
had  ceased,  the  water  collected  was  removed,  measured  and  sent  to 
the  chemical  laboratory.  The  amount  of  the  drip  was  6.9  litres.  Sub- 
sequent applications  were  made  in  like  manner  on  August  7,  14  and  21. 
It  would  have  been  more  satisfactory  if  uniform  amounts  of  water 
had  been  applied,  but  this  was  neglected  and  the  waters  collected 
gradually  increased.  The  second  spray  gave  8.96  litres,  the  third  9.06 
litres,  and  the  fourth  12.12  litres. 

On  completion  of  the  spraying  as  previously  planned,  it  was  de- 
cided to  dispense  with  the  cover  and  collect  the  waters  from  rains 
thru  the  rest  of  the  season,  as  with  tree  No.  33.  Following  this  plan 
the  waters  of  eleven  rains  were  collected  between  August  24  and  Oc- 
tober 4.  The  analytical  results  for  both  spray  waters  and  rain  waters 
are  brought  together  in  the  following  tabulation : 

Chemical  Determinations  of  Waters  Collected  from  Tree  Number  34. 


Soluble  constituents  of  drip  waters 

Sediment  filtered  from  drip  waters 

Serial 

Date 

Amount 
of 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Arsenic  in 

Insoluble  copper 

Insoluble  arsenic 

Vumhpr 

J    j 

ipr      „  of 

Total 

Milligrams 

Total 

Milligrams 

As203 

Total 

Milligrams 

Total       Milligrams 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams     Per  litre 

34 

July       31 

6.39 

412.0 

64.4 

36.0 

5.6 

1.1 

971.6 

152.0      143.5 

22.4 

34  a 

August    7 

8.96 

241.6 

26.9 

30.0 

3.3 

3.6 

896.8 

100.8 

61.2         6.8 

34  b 

August  14 

9.06 

81.2 

8.9 

26.3 

2.9 

2.3 

398.4 

43.9   i     88.2         9.7 

34  c 

August  21 

12.12 

90.0 

7.4 

16.3 

1.3 

Trace 

106.8 

8.8 

21.4         1.7 

34  d 

August  24      1  .  50 

38.8 

25.8 

1.3 

0.8 

Trace 

78.4 

52.2 

18.2 

12.1 

34  e 

August  26     14.96 

360.4 

24.0 

20.0 

1.3 

4.7        246.4        16.4        54.6 

3.6 

34  f 

Sept.        3      1.25 

26.0 

20.8 

Too  dark 

Trace 

142.0 

113.6        23.5        18.8 

34  g 

Sept.      13      1.53 

56.4 

36.8 

Too  dark 

Trace 

50.4 

32.9        88.8       58.4 

34  h 

Sept.      20      1.70 

50.4    |    29.6 

0.20 

Trace 

282.8 

166.3 

66.5       39.3 

34  i 

Sept.      22      9.10 

177.6 

19.5 

Neutral 

Trace 

182.4 

20.0        35.5 

5.0 

34  j 

Sept.      26      0.75 

28.4 

37.8 

Neutral 

Trace 

84.0 

112.0 

40.6 

54.1 

34  k 

Sept.      27 

5.10 

49.2 

9.6 

Neutral 

Trace 

100.8 

19.7 

45.5 

8.9 

341 

Sept.      29    12.70      231.2 

18.2 

Neutral 

3.5 

84.0 

6.6 

46.2 

3.6 

34  m 

October  1     14.82 

194.0 

13.0 

Neutral 

2.9          99.6 

6.7 

17.5 

1.1 

34  n 

October  4      2.90 

98.0 

33.8 

Too  dark 

2.4 

56.0 

19.3 

Trace 

1909] 


BORDEAUX  MIXTURE 


257 


Here  again,  soluble  copper  is  found  in  the  first  drip  waters  col- 
lected, and  in  all  succeeding  waters.  The  amount  of  copper  per  litre 
decreases  steadily  for  the  four  applications  of  water  as  spray,  then 
with  the  first  rain  shows  a  considerable  increase,  which  is  maintained 
with  some  degree  of  uniformity  to  the  end  of  the  season.  The  alka- 
linity of  the  waters  decreases  steadily,  reaching  neutrality  early  in  Sep- 
tember. Arsenic  in  solution  is  present  in  very  small  quantities,  mostly 
traces  only  in  all  waters.  The  quantities  of  insoluble  copper  and  ar- 
senic in  the  residues,  fluctuate  considerably,  but  both  are  present  in  all 
waters. 

Injury  to  foliage  on  this  tree  was  almost  negligible.  Casual  exam- 
ination revealed  none,  but  on  close  inspection  a  few  small  marginal 
spots  were  found.  These  appeared  after  the  cover  had  been  discon- 
tinued and  under  the  influence  of  the  first  rains,  but  were  so  few  in 
number  that  they  hardly  deserve  mention.  Save  for  injury  by  the 
skeletonizer  to  some  of  the  leaves  expanded  after  application  of  the 
Bordeaux  mixture,  the  foliage  of  the  tree  was  very  nearly  perfect  at 
the  close  of  the  season.  As  on  tree  33,  a  few  small  leaves  became  yel- 
low, and  fell  during  the  season.  All  remaining  leaves  were  picked 
October  13  and  preserved,  for  determination  of  copper  still  adhering. 

TREE  NUMBER  35 

Sprayed  July  25  in  the  same  manner  as  trees  33  and  34  with  a 
Bordeaux  mixture  made  on  the  same  formula.  The  funnel  was  then 
adjusted  and  cover  provided  to  protect  from  rain  and  dew.  One  week 
from  the  application  of  Bordeaux,  August  1,  the  tree  was  sprayed 
with  cistern  water  and  this  was  repeated  at  intervals  of  one  week  until 
the  ninth  application  September  26.  No  further  spraying  was  done 
and  covering  was  discontinued.  The  tree  was  subjected  to  two  rains 
October  4  and  20,  and  the  drip  waters  were  saved  and  analyzed.  The 
chemical  data  obtained  from  the  waters  are  given  in  tabular  form  be- 
low. 

Chemical  Determinations  from  Waters  Collected  from  Tree  Number  35. 


Soluble  constituents  of  drip  waters 

Sediment  filtered  from  drip  waters 

Serial 

Date 

Amount 
of 

Copper 

Alkalinity   in   terms 
of  calcium  oxide 

Arsenic  in 

Insoluble  copper 

Insoluble  arsenic 

Number 

J     • 

i              nf 

Total 

Milligrams 

Total 

Milligrams 

As2ba 

Total 

Milligrams 

Total 

Milligrams 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

35 

August     1 

9.47 

79.6 

8.4 

141.8 

14.9 

6.3 

1055.2 

111.4 

36.5 

3.8 

35  a 

August    8 

9.70 

201.2 

20.6 

94.9 

9.7 

Trace 

1174.0 

121.0 

49.2 

5.0 

35  b 

August  15 

12.94 

320.8 

24.7 

67.3 

5.2 

Trace 

870.8 

67.2 

45.5 

3.5 

35  c 

August  22 

11.43 

67.6 

5.9 

127.7 

11.1 

Trace 

527.2 

46.1 

38.3 

3.3 

35  d 

August  29 

11.48 

174.0 

15.1 

4.7 

0.4 

Trace 

321.6 

28.0 

35.0 

3.0 

35  e 

Sept.        5 

11.17 

128.4 

11.4 

85.6 

7.6 

Trace 

182.0 

16.2 

49.0 

4.3 

35  f     Sept.      12 

11.50 

656.8 

57.1 

5.8 

0.5 

Trace 

89.6 

7.7 

46.2 

4.0 

35  g 

Sept.      20 

10.00 

879.6 

87.9 

18.8 

1.8 

Trace 

303.6  I     30.3 

77.0 

7.7 

35  h 

Sept.      26 

10.65 

652.8 

61.2 

40.9 

3.8 

Trace 

46.8 

4.4 

13.3 

1.2 

Too 

35  i 

Oct.         8 

3.00 

32.4 

10.8 

Too  dark 

dark 

Trace 

122.0 

40.6 

33.6 

11.2 

35  j 

Oct.       20 

15.90 

903.2 

56.7 

Too  dark 

Too 

dark 

10.6 

53.6 

3.3 

20.3 

1.2 

258 


BULLETIN  No.   135 


[May 


Soluble  copper  was  present  in  all  waters  from  first  to  last.  In  the 
first  lot,  August  1,  the  amount  is  small,  and  still  smaller  in  the  fourth 
lot  collected  August  22.  The  last  three  sprays  give  considerably  in- 
creased amounts,  and  the  maximum  appears  in  the  lot  of  September 
20.  Alkalinity  fluctuates,  but  is  apparently  more  persistent  than  in  the 
waters  from  preceding  trees.  Soluble  arsenic  was  present  in  all 
waters,  but  except  for  the  first  and  last,  only  as  a  trace.  All  residues 
from  filtering  yielded  appreciable  but  fluctuating  amounts  of  insoluble 
copper  and  arsenic. 

Injury  to  foliage  on  tree  35  was  as  slight  as  on  No.  34.  Here  it 
took  the  form  of  burned  tips,  but  so  few  leaves  were  thus  marked 
that  the  injury  would  easily  escape  notice. 

TREE  NUMBER  36 

This  tree  duplicated  Numbers  34  and  35  in  equipment  and  cover, 
as  well  as  in  the  manner  and  material  of  preliminary  treatment.  The 
spraying  was  done  and  the  tree  prepared  July  28.  Subsequent  treat- 
ment was  scheduled  to  include  four  applications  of  cistern  water  at 
seven  day  intervals ;  the  fourth  spray  was  to  be  followed-  by  an  inter- 
val of  28  days,  and  then  a  final  spraying  with  water.  This  procedure 
was  carried  out  in  order  to  test  the  relation  between  time  intervals 
and  amount  of  soluble  copper  washed  off  by  spray.  The  chemical  re- 
sults tabulated  below,  indicate  that  copper  in  soluble  form  did  accumu- 
late during  the  long  interval : 


Chemical  Determinations  from  Waters  Collected  from  Tree  Number  36. 


F  Serial 
Number 

Date 

Amount 
of  i 
drip 

Soluble  constituents  of  drip  waters 

Sediment  filtered  from  drip  waters 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Arsenic  in 
terms  of 
As203 

Insoluble  copper 

Insoluble  arsenic 

Total 
Milligrams 

Milligrams 
Per  litre 

Total 

Milligrams 

Milligrams 
Per  litre 

Total 
Milligrams 

Milligrams 
Per  litre 

Total 
Milligrams 

Milligrams 
Per  litre 

36 
36  a 
36  b 
36  c 
36  d 

August    4 
August  11 
August  18 
August  25 
Sept.      22 

9.99 
11.11 
10.55' 
9.68 
11.50 

182.0 
237.6 
130.0 
117.6 
509.2 

18.2 
21.3 
12.3 
12.1 
44.2 

119.6 
148.0 
35.6 
42.4 
Too  dark 

11.9 
13.3 
3.3 
4.3 

7.5 
3.7 
1.3 
1.1 
7.9 

1214.4 
309.6 
211.2 
160.0 
726.0 

121.5 

27.8 
20.0 
16.4 
63.1 

90.6 
30.6 
32.9 
31.8 
159.2 

9.0 
2.7 
3.1 
3.2 
13.8 

The  waters  of  the  final  spray  applied  at  the  end  of  a  28  day  inter- 
val contained  44.2  milligrams  of  soluble  copper  per  litre.  This  is  more 
than  twice  the  amount  per  litre  shown  from  the  first  and  second  lots 
of  water  and  more  than  3*/2  times  the  quantities  determined  in  the 
third  and  fourth  lots,  all  these  being  taken  at  7  day  intervals.  Com- 
puting the  amounts  of  copper  proportionate  to  the  amounts  of  water 
collected,  the  application  following  the  long  interval  still  has  more  than 
twice  as  much  copper  as  is  found  in  the  first  and  second,  and  over  three 
times  the  amount  in  the  third  or  fourth. 

Arsenic  in  solution  appears  in  descending  scale  for  the  four  waters 
at  7  day  intervals,  and  then  increases,  after  the  long  interval,  to  an 


1909] 


BORDEAUX  MIXTURE 


259 


amount  in  excess  of  that  found  in  the  first  water ;  the  amount  de- 
creased with  regularity  to  the  fourth  spraying  and  then,  after  the  long 
interval,  increased  to  nearly  four  times  the  amount  in  the  water  from 
the  fourth  spraying.  Insoluble  arsenic  decreased  in  an  irregular  man- 
ner for  the  short  periods,  but  in  the  last  water,  collected  after  the  long 
interval,  it  was  found  in  quantity  greater  than  that  of  any  two  of  the 
earlier  lots. 


FIG.  5.     Tree  No.   36.     Cover  adjusted,   curtain  down. 

Foliage  on  this  tree  remained  very  nearly  perfect.  There  were 
no  brown  spots,  but  search  brought  to  view  a  few  leaves  that  had 
slightly  burned  tips.  When  the  leaves  were  finally  gathered  October 
20  they  were  still  conspicuously  blue  with  Bordeaux  mixture. 

Tree  No.  36  equipped  with  cover,  and  with  curtain  down,  is 
shown  in  Figure  5.  Figure  6  shows  the  same  tree  without  cover  and 
with  curtain  raised  to  show  adjustment  of  jar.  From  photographs 
August  4,  1907. 


260  BULLETIN  No.   135  [May 

SUMMARY  OF  RESULTS  FROM  THE  FOUR  TREES 

The  striking  features  of  the  records  obtained  from  the  four  trees 
that  have  been  considered  are : 

1.  The  constant  presence  of  copper  in  solution.  It  was  found  in 
all  waters  examined,  and  except  for  the  second  rain  on  tree  No.  33 
from  which  the  amount  of  water  was  too  small  for  proper  analysis,  the 
quantities  were  measurable.  It  is  true  that  the  quantities  are  small, 


FIG.    6.     Tree    No.    36.     Cover   removed.     Curtain    raised    to    show    adjustment    of 
funnel  to   drip   jar. 

giving  solutions  that  range  between  1  part  copper  in  11,000  parts  water 
and  1  part  copper  in  170,000  parts  water;  but  it  must  be  remembered 
that  all  the  water  collected  did  not  come  in  contact  with  the  leaves  and 
that  much  that  did  made  very  hasty  passage  and  probably  took  up  very 
little  copper,  so  that  while  solutions,  as  represented  by  the  bulk  of  drip 
waters,  are  much  diluted,  it  is  reasonable  to  assume  that  on  leaf  sur- 


1909]  BORDEAUX  MIXTURE  261 

faces,  where  the  fungicidal  action  is  wanted,  the  solutions  are  more 
concentrated  and  fully  able  to  perform  the  office  intended,  namely, 
prevention  of  infection  by  germinating  spores  of  fungi.  The  most 
dilute  solution  found,  1 :170,000,  is  relatively  quite  concentrated  if  we 
compare  it  with  a  solution  2  or  3  to  10,000,000  which  is  stated  by 
Millardet  to  be  effective  as  a  preventive  of  infection  by  Peronospora. 
Fluctuations  in  the  amount  of  copper  in  solution  are  to  be  ex- 
pected and  are  influenced  by  many  things,  among  which  may  be  men- 
tioned, direction  of  the  storm,  presence  or  absence  of  wind,  velocity 
of  wind,  size  of  rain  drops  and  duration  of  storm.  The  important 
point  is  that  copper  in  soluble  form  is  always  present. 

2.  The  appearance  of  soluble  copper  soon  after  the  Bordeaux  had 
been  sprayed  on  the  leaves.  The  mixtures  used  in  the  experiments 
recorded  contained  no  copper  in  solution  at  the  time  of  spraying.  With 
each  of  the  four  trees  the  interval  between  application  of  Bordeaux 
and  the  first  rain  or  spray  of  water  was  seven  days.  Soluble  copper 
was  found  in  these  first  waters  collected  under  each  of  the  four  trees 
and  in  measurable  quantities.  Free  calcium  oxide  was  also  present  in 
quantity  in  these  waters.  This  finding  is  directly  contradictory  to  the 
statement  by  Millardet  and  Gayon  and  others  that  no  copper  becomes 
soluble  until  all  free  lime  has  been  washed  away  or  converted  into  in- 
soluble carbonate.  It  is  also  opposed  to  the  results  obtained  from  the 
laboratory  experiments  already  recorded,  in  which  Bordeaux  mixtures 
m_  glass  dishes,  both  continuously  dry  and  intermittently  wet,  yielded 
no  soluble  copper  after  65  days,  and  in  which  two  sprayed  trees,  one 
kept  dry  the  other  frequently  moistened  and  after  45  days  washed  as 
thoroly  as  possible  with  neutral  distilled  water,  gave  no  trace  of  cop- 
per in  soluble  farm. 

3.  Examination  of  the  results  recorded,  suggests  another  feature 
that  is  of  sufficient  importance  to  deserve  specific  mention,  and  that  is 
the  evidently  slow  solubility  of  the  copper  deposited  in  the  Bordeaux 
mixture.     The  copper  in  solution  fluctuates  with  different  waters  and 
at  different  times,  but  the  amounts  are  always  small,  never  in  such  ex- 
cess as  would  indicate  other  than  very  slow  solubility.     Tree  No.  33 
was  in  commission  for  84  clays.     The  amount  of  copper  per  litre  in 
the  water  from  the  last  rain,  75  days  from  the  date  of  spraying,  was 
nearly  double  the  amount   in  the  first  water  collected  7   days   after 
spraying.     The  waters  of  October   1  and  4  contained  approximately 
the  same  as  the  waters  of  August  7  and  8.     The  maximum  amount  per 
litre  appeared  September  26,  or  67  days  from  date  of  spraying.     This 
slow  solubility  is  one  of  the  most  valuable  characteristics  of  rightly 
made  Bordeaux.     The  copper  becomes  soluble  with  sufficient  rapidity 
to  maintain  the  defensive  power,  but  not  rapidly  enough  to  dissipate 
quickly  the  reserve,  and  thus  the  action  is  prolonged  for  a  long  period. 

4.  A  feature  conspicuous  in  each  of  the  four  trees  under  consid- 
eration  was  the  very  great   adhesiveness  of   the   Bordeaux   mixture. 
Notwithstanding  the  considerable  quantity  of  water  passed  over  the 
leaves,  the  blue  color  was  remarkably  persistent,  particularly  on  the 
trees  that  were  artificially  sprayed.     The  tree  without  cover  apparently 


262  BULLETIN  No.   135  [May 

lost  more  of  the  Bordeaux  than  did  those  with  covers,  but  even  here 
the  leaves  were  conspicuously  coated  when  picked  October  13,  84  days 
from  the  date  of  spraying.  The  tree  was  in  some  degree  protected 
from  wind  by  the  funnel  but  otherwise  the  exposure  was  complete. 

5.  A  fifth  feature  worthy  of  comment  is  the  almost  perfect  con- 
dition of  the  leaves  notwithstanding  the  extremely  heavy  application 
of  Bordeaux.  In  no  case  was  there  sufficient  injury  to  attract  atten- 
tion ;  such  as  was  found  by  searching,  consisted  of  small  marginal 
burned  spots  and  a  few  burned  tips.  Numerous  heavily  coated  leaves 
remained  without  blemish  until  the  close  of  the  season. 

TREE  NUMBER  49 

This  tree  was  provided  with  appliances  for  catching  drip  waters 
similar  to  those  already  described.  The  spraying  was  done  August  23 
in  the  same  manner  as  for  the  other  trees,  but  with  a  Bordeaux  mix- 
ture combined  with  Arsenate  of  Lead  instead  of  Paris  green.  The 
formula  was  as  follows : 

Copper  sulphate 4  pounds 

Fresh-slaked  -lime 4  pounds 

Swift's  Arsenate  of  Lead 3  pounds 

Water ' 50  gallons 

About  the  time  this  work  was  instituted,  the  opinion  was  current 
among  orchard  owners  that  arsenate  of  lead  could  not  be  successfully 
combined  with  Bordeaux  mixture.  It  was  said  that  when  combined 
the  "one  neutralized  the  other"  and  that  both  fungicidal  and  insectici- 
dal  value  was  destroyed.  Who  first  disseminated  this  opinion  or  upon 
what  observations  it  was  based  is  not  known.  However,  the  fre- 
quency with  which  questions  regarding  the  combination  of  these  two 
compounds  were  asked  made  it  desirable  that  definite  information  be 
secured  through  direct  experiments.  To  this  end  tree  Number  49  was 
sprayed  with  a  combined  mixture,  made  after  the  formula  given  above. 
Full  exposure  to  dew  and  rain  were  allowed  as  with  tree  No.  33,  but 
the  two  trees  are  not  strictly  comparable  because  tree  No.  49  received 
a  Bordeaux  spray  33  days  later  than  did  No.  33  and  was  subjected  to 
the  waters  of  only  about  half  the  number  of  rains.  When  the  mixture 
for  use  on  tree  No.  49  was  prepared,  two  hydrometer  tubes  were  filled, 
and  the  settling  qualities  tested.  In  this  regard  the  arsenate  of  lead 
mixture  exhibits  a  very  slight  advantage  over  the  Paris  green  mixture 
for  the  first  day,  and  a  somewhat  greater  advantage  at  the  end  of  the 
second  day.  The  extreme  of  difference,  however,  is  too  small  to  be  of 
importance  from  a  practical  standpoint.  Between  August  23  and  Oc- 
tober 4,  the  leaves  of  tree  No.  49  were  washed  by  the  waters  of  11 
rains,  giving  precipitation  to  the  amount  of  3.3  inches,  and  the  total 
of  drip  waters  collected  amounted  to  65  litres.  Soluble  copper  was 
present  in  all  waters  in  measurable  quantities.  The  amounts  per  litre 
fluctuate  rather  more  widely  than  do  the  amounts  in  the  waters  from 
tree  No.  33,  but  the  averages  are  not  widely  separated,  being  24.2 
milligrams  per  litre  for  tree  No.  49  and  29.18  milligrams  per  litre  for 
tree  No.  33.  It  is  significant  to  note  that  the  first  rain  came  in  less 


1909] 


BORDEAUX  MIXTURE 


263 


than  12  hours  after  spraying  was  completed;  (a  shower  of  20  minutes 
duration  giving  rain  fall  of  0.06  inch  and  that  the  waters  collected  con- 
tain 2.8  milligrams  of  soluble  copper  per  litre.  This  amount  is  small, 
but,  coming  as  it  does  in  less  than  12  hours  from  deposition  of  a  mix- 
ture containing  no  soluble  copper,  the  result  is  interesting. 

Arsenic  in  solution  was  detected  in  all  waters,  but  in  mere  traces 
only.  Insoluble  arsenic  was  recovered  from  all  waters  and  in  consid- 
erably greater  quantities  than  were  shown  to  be  present  in  correspond- 
ing waters  from  tree  No.  33.  On  the  other  hand,  insoluble  copper  was 
much  more  abundant  in  waters  from  tree  No.  33  than  from  those  from 
No.  49.  Determinations  made  from  the  waters  collected  follow  in 
tabular  form: 


Chemical  Determinations  from  Waters  Collected  from  Tree  Number  49. 


Soluble  constituents  of  drip  waters 

Sediment  filtered  from  drip  waters 

Serial 

Date 

Amount 
of 

Copper 

Alkalinity   in   terms 
of  calcium  oxide 

Arsenic  in 

Insoluble  copper 

Insoluble  arsenic 

Total 

Milligrams 

Total 

Milligrams 

As20s 

Total 

Milligrams 

Total 

Milligram 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Milligrams 

Per  litre 

Mere 

49 

August  24 

1.64 

4.6 

2.8 

45.1 

27.5 

trace 

36.1 

22.0 

Trace 

49  a 

August  27 

13.92 

74.4 

5.3 

154.8 

11.1 

72.7 

5.2 

48.1 

3.4 

49  b 

Sept.       3 

1.25 

104.4 

83.5 

Too  dark 

38.2 

30.5 

24.7 

19.7 

49  c 

Sept.      12 

1.70 

61.3 

36.0 

Too  dark 

.... 

25.4 

14.9 

26.1 

15.3 

49  d 

Sept.      20 

1.80 

9.8 

5.4 

Too  dark 

28.7 

15.9 

22.5 

12.5 

49  e 

Sept.      22 

9.14 

184.4 

20.1 

Too  dark 

45.6 

4.9 

28.4 

3.1 

49  f 

Sept.      26 

.80 

41.0 

51.2 

Too  dark 

9.1 

11.3 

15.5 

19.3 

49* 

Sept.      27 

5.45 

53.4 

9.8 

Too  dark 

64.3 

11.7 

30.9 

5.6 

49  h 

Sept.      29 

10.60 

238.8 

22.5 

Neutral 

74.8 

7.0 

46.5 

4.3 

49  i 

October  1 

15.88 

93.1 

5.8 

Neutral 

86.7 

5.4 

54.1 

3.4 

49  j 

October  6 

3.02 

72.4 

24.0 

Too  dark 

29.4 

9.7 

23.6 

7.7 

The  behavior  of  the  Bordeaux  arsenate  of  lead  combination  as 
observed  on  this  tree  was  very  satisfactory.  The  mixture  appears  to 
possess  exceptional  adhesiveness  and  to  part  with  its  copper  and  ar- 
senic at  such  a  slow  rate  that  its  protective  influence  is  prolonged  to 
the  end  of  the  season.  The  proved  presence  of  soluble  copper,  in  all 
waters,  indicated  a  continuous  supply  of  this  element  in  readiness  for 
action  against  infection  by  fungi,  and  arsenic  is  retained  in  amounts 
sufficient  to  insure  protection  against  insects.  Nothing  was  observed 
during  the  season  to  indicate  that  any  loss  of  fungicidal  or  insecticidal 
value  followed  the  combination  of  the  compounds  in  question.  On  the 
contrary  continuous  observation  led  to  the  belief  that,  so  far  as  could 
be  judged  from  the  one  experiment,  the  combination  of  Bordeaux  with 
arsenate  of  lead  has  decided  advantages  over  the  Bordeaux  Paris  green 
mixture.  The  one  valid  objection  is  on  the  basis  of  cost,  but  it  is  ex- 
pected that  further  trial  may  demonstrate  that  the  additional  expense 
is  more  than  balanced  by  prolonged  adhesiveness,  efficiency,  and 
entire  absence  of  injury  to  foliage. 


264  BULLETIN  No.   135  [May 

INVESTIGATIONS  IN  1907 

In  1906  spraying  the  trees  from  which  drip  waters  were  collected 
began  July  21.  This  is  rather  late  in  the  season,  and  the  question  arose 
as  to  whether  applications  applied  earlier  in  the  summer  would  show 
an  equal  degree  of  adhesiveness  and  as  little  injurious  effect  upon 
foliage.  It  was  also  desired  to  test  somewhat  further  the  relative  in- 
fluence of  meteoric  waters  and  artificially  applied  spray ;  to  test  the 
effect  of  maintaining  an  excess  of  calcium  oxide  by  additional  spray- 
ing with  milk  of  lime  and  also  several  other  ^questions  suggested  by  the 
results  al  ready  a  recorded. 

For  the  season  of  1907,  therefore  a  considerably  extended  series 
of  experiments  was  projected  and  carried  out.  Funnels  and  jars  were 
provided,  together  with  other  necessary  equipment,  for  28  trees,  which 
were  used  in  pairs,  for  14  experiments.  Each  experiment  was  given 
a  number  and  the  two  trees  were  distinguished  by  the  letters  A  and  B. 
With  two  exceptions  the  trees  of  each  pair  were  treated  exactly  alike. 
Under  the  Numbers  1107  A  and  B  and  1207  A  and  B  the  individuals 
were  differently  treated,  as  will  be  explained  later.  The  season  proved 
to  be  a  wet  one ;  rains  were  frequent  and  abundant  and  the  resources 
of  the  department  were  seriously  taxed  in  handling  the  large  amount 
of  water.  The  experiments,  however,  were  carried  thru  to  the 
close  of  the  season  with  very  few  minor  accidents.  A  portion  of  the 
trees  used  for  the  experiments  of  1907  are  shown  in  Figure  7. 

SCHEDULE  OF  EXPERIMENTS 

No.  507 — two  trees — A  and  B.  Sprayed  heavily  with  standard 
Bordeaux-Paris  green  mixture.  Exposed  to  all  atmospheric  condi- 
tions. To  test  the  effect  of  meteoric  waters  on  solubility  of  copper 
and  the  removal  of  excess  lime.  Duplicating  No.  33  of  the  preceding 
year. 

No.  607 — two  trees — A  and  B.  Preliminary  spray  as  for  507. 
Protection  from  meteoric  waters.  Sprayed  with  cistern  water  once 
each  week.  For  comparison  with  507  to  test  the  relative  effect  of  nat- 
ural rain  and  water  applied  artificially  as  spray  at  regular  intervals. 

No.  707 — two  trees — A  and  B.  Preliminary  spray  as  for  507. 
Exposed  to  all  atmospheric  conditions.  Sprayed  with  milk  of  lime 
4-50  once  each  week.  To  test  the  influence  of  maintenance  of  excess 
lime  on  solubility  of  copper. 

No.  807 — two  trees — A  and  B.  No  spray  of  Bordeaux.  Ex- 
posed to  all  atmospheric  conditions.  Collect  all  drip  from  rains.  Spray 
with  milk  of  lime  4-50  once  each  week.  To  test  the  effect  on  foliage 
of  milk  of  lime  only.  Compare  with  707. 

No.  907 — two  trees — A  and  B.  Preliminary  spray  as  for  507. 
Protection  from  meteoric  waters,  spray  with  cistern  water  once  each 
week.  Every  Tuesday.  Spray  with  milk  of  lime  4-50  each  week. 
Every  Friday.  To  test  the  effect  of  water  as  spray,  in  connection  with 
milk  of  lime,  in  comparison  with  rain  and  milk  of  lime. 

1007 — two  trees — A  and  B.  Preliminary  spray  as  for  507.  Pro- 
tection from  meteoric  waters.  Spray  once  each  week  with  water 


1909] 


BORDEAUX  MIXTURE 


265 


266  BULLETIN  No.  135  [May 

saturated  with  carbon  dioxide.     To  test  the  influence  of  carbon  diox- 
ide, in  solution  in  water,  on  the  solubility  of  copper. 

1107 — two  trees  A  and  B.  Preliminary  spray  as  for  507.  Pro- 
tection from  meteoric  waters.  After  an  interval  of  several  days. 

A.  Spray  with  10  litres  of  cistern  water,  allow  the  tree  to  dry. 
Collect  the  water.     Repeat  as  many  times  as  possible  during  the  day. 
To  test  the  rate  of  removal  of  soluble  copper  under  the  action  of  con- 
tinuous spraying.     Repeat  on  a  later  date. 

B.  Spray  with  water  to  keep  foliage  moist  all  day  with  as  little 
drip  as  possible.     Remove  drip  at  evening  and  then  spray  with  about 
10  litres  of  water  and  remove  drip.     Repeat  on  later  date.     To  test 
long  continuance  of  moist  conditions. 

1207 — two  trees,  A  and  B.  No  spray  of  Bordeaux.  Protection 
from  meteoric  waters. 

A.  Spray  as  for  1107  A,  but  use  a  solution  of  copper  sulphate 
50  mg  to  the  gallon.     In  previous  work,  drip  waters  in  several  in- 
stances contained  50  mg  or  more  per  gallon.     This  is  to  test  the  action 
on  foliage  of  such  a  solution  artificially  applied.     The  solution  is  quite 
dilute.     1 :75707+. 

B.  Sprayed  as  for  A  but  with  a  stronger  solution  9.071  grams  of 
copper  sulphate  to  the  gallon  or   1 :417-j-     To  test  the  effect  of  a 
stronger  solution  and  to  determine  the  copper  content  of  the  drip. 

1307 — two  trees — A  and  B.  Preliminary  spray  as  for  507.  Pro- 
tection from  meteoric  waters.  Spray  with  distilled  water  once  each 
week.  To  test  distilled  water  as  compared  with  cistern  water  in  its 
effect  on  Bordeaux  on  leaves. 

1407 — two  trees — A  and  B.  Preliminary  spray  with  standard  for- 
mula Bordeaux  made  with  air-slaked  lime.  Exposed  to  atmospheric 
conditions.  To  test  action  on  foliage  and  adhesiveness  of  Bordeaux 
made  with  air-slaked  lime. 

1507 — two  trees — A  and  B.  Preliminary  spray  with  Bordeaux 
made  on  the  formula  4-1-^-50.  Reducing  the  lime  to  1  pound.  Ex- 
posed to  atmospheric  conditions.  To  test  effect  on  foliage  of  Bor- 
deaux with  reduced  amount  of  lime. 

1607 — two  trees — 'A  and  B.  Preliminary  spray  with  Bordeaux 
made  after  the  formula  4-^-^4-50.  Reducing  the  lime  to  ''l/2  pound. 
Exposed  to  atmospheric  conditions.  To  test  this  extreme  reduction  in 
the  lime. 

1707 — two  trees — A  and  B.  Preliminary  spray  with  Bordeaux 
mixture  with  lime  reduced  to  1  pound.  4-1-^4-50.  Protection  from 
meteoric  waters.  Spray  once  each  week  with  water  saturated  with 
carbon  dioxide.  To  test  action  of  carbon  dioxide,  in  solution  in  water, 
on  Bordeaux  made  with  small  amount  of  lime. 

1907 — two  trees — A  and  B.  Preliminary  spray  with  Bordeaux 
arsenate  of  lead  combination,  after  the  formula,  4-4-3-50,  using 
Swift's  paste  arsenate  of  lead.  Exposed  to  atmospheric  conditions. 
To  test  the  action  on  foliage,  adhesiveness  and  rate  of  solubility  of 
copper  in  this  combination. 


1909]  BORDEAUX  MIXTURE  267 

TREES  507  A  AND  507  B  COMPARED  WITH  No.  33  OF  1906 

The  three  trees,  No.  33  of  1906,  and  Nos.  507  A  and  507  B  in 
1907  were  treated  in  exactly  the  same  manner  in  regard  to  equipment, 
and  preliminary  spray.  In  length  of  time  under  observation,  and  in 
amount  of  rainfall  to  which  the  trees  were  subjected,  there  is  a  wide 
difference  between  the  two  seasons.  In  1906,  tree  No.  33  was  ob- 
served for  75  days ;  in  1907,  trees  507  A  and  B  were  observed  for  137 
days  or  1.82  times  as  many  days.  Tree  No.  33  received  7.3  inches  of 
rain  from  21  storms,  while  the  trees  in  1907  received  13.36  inches 
from  24  storms.  The  amount  of  water  collected  in  1907  was  nearly 
double  the  amount  for  1906.  The  average  number  of  litres  in  each 
lot  of  water  was  6.2  for  1906,  and  11.75  for  1907.  All  waters  from 
tree  No.  33  contained  soluble  copper  altho  in  one  lot  there  was  only  a 
trace. 

From  507  A,  there  was  one  lot  containing  a  trace  only;  from 
507  B,  one  lot  was  lost  thru  accident.  With  these  exceptions  soluble 
copper  was  present  in  measurable  amounts.  The  quantities,  however, 
are  much  higher  for  1906  than  for  either  of  the  trees  in  1907.  The 
maxima  in  milligrams  per  litre  are  85  for  1906,  and  70  for  1907;  the 
minima  are  8.9  for  1906,  and  0.7  for  1907.  The  averages  are  23.5 
milligrams  per  litre  for  1906,  and  9.2  for  1907,  or  stated  proportion- 
ately there  was  2^  times  as  much  soluble  copper  per  litre  of  water  in 
1906  as  there  was  in  1907.  It  has  already  been  mentioned  that  small 
quantities  of  water  contained  proportionately  larger  amounts  of  cop- 
per in  solution  per  litre,  than  large  quantities,  and  this  fact  is  strongly 
emphasized  in  comparing  the  records  under  consideration. 

Other  seasonal  differences  that  may  be  mentioned  are  intervals  be- 
tween rains,  and  character  of  storms.  The  longest  intervals  are  nine 
days  in  1906  and  21  days  in  1907;  the  least  intervals  are  0  in  1906  and 
12  hours  in  1907;  the  averages  are  3.16  days  for  1906  and  5.6  days  for 
1907.  Storms  for  the  two  seasons  classify  as  follows : 

1906       1907 

Local  showers 11  6 

Electrical  storms 7  14 

Protracted  rains 3  4 

It  has  been  frequently  suggested  that  there  might  be  a  definite 
relation  between  the  character  of  the  storm  and  the  conversion  of  cop- 
per into  soluble  forms,  with  subsequent  injury  to  foliage.  Statements 
have  been  made  to  the  effect  that  electrical  phenomena  often  preceded 
the  appearance  o,f  injury  to  foliage,  and  there  has  been  an  effort  to  con- 
nect the  two.  These  things  have  been  in  mind  during  this  investiga- 
tion, and  it  may  be  said,  that  up  to  the  present  time,  no  evidence  has 
been  secured  that  points  to  electrical  disturbances  as  in  any  way  re- 
sponsible for  the  passing  of  copper  into  solution  and  the  following  in- 
jury to  foliage.  The  classification  of  storms,  to  which  the  trees  used 
were  subjected,  shows  that  in  1907  there  were  twice  as  many  electrical 
storms  as  in  1906,  yet  a  decidedly  larger  amount  of  copper  was  found 
in  1906  than  in  1907.  The  same  wide  difference  in  amounts  of  soluble 
copper,  present  in  the  waters  from  the  trees  of  the  two  seasons,  ap- 


268 


BULLETIN  No.   135 


[May 


pears  also  in  the  determinations  of  insoluble  copper  found  in  the  resi- 
dues. The  average  amount  in  the  waters  of  1906  is  246.7  milligrams, 
with  an  average  per  litre  of  54.3  milligrams,  while  from  the  waters  of 
1907  there  was  recovered  an  average  of  155.5  milligrams  with  an  aver- 
age per  litre  of  20  milligrams.  It  is  evident  that  the  copper  of  the 
Bordeaux  used  in  1906  was  more  readily  soluble  and  less  tenaciously 
held  by  the  leaves  than  was  the  case  in  1907  and  it  is  probable  that 
more  than  one  cause  has  operated  to  bring  about  this  difference. 
There  may  have  been  undiscovered  differences  in  the  mixtures  as 
made  and  applied.  While  every  precaution  was  taken  in  making  and 
in  application,  the  lime  in  one  case  may  have  been  a  little  less  fresh,  or 

Chemical  Determinations  from  Waters  Collected  from  Tree  507  A. 


Soluble  constituents 

Serial 
JN  umber 

Date 

Amount 
of 

Copper 

Alkalinity    in 
terms  of 

Insoluble 
copper 

drip 

calcium   oxide 

Total 

Per  litre 

Total 

Per  litre 

Total 

Per  litre 

507  A    1 

June        22 

1.73 

106.0 

61  2 

94.6 

54.6 

290.7 

168.0 

507  A    2 

June        24 

41.37 

361.1 

8.7 

743.7 

17.9 

1186.2 

28.6 

507  A    3 

July          1 

2.44 

14.1 

5.7 

86.7 

35.5 

216.1 

88.5 

507  A    4 

July          6 

9.58 

Trace 

290.6 

30.3 

414.5 

43.2 

507  A    5 

July    9,  10 

24.88 

200.0 

8.0 

439.6 

17.6 

392.9 

15.7 

507  A    6 

July  10,  11 

9.79 

84.5 

8.6 

154.4 

15.7 

117.8 

12.0 

507  A    7 

July  14,  15 

24.21 

62.6 

2.5 

367.9 

15.2 

139.5 

5.7 

507  A    8 

July         17 

6.60 

56.0 

8.5 

88.8 

13.4 

102.1 

15.4 

507  A    9 

July         26 

2.22 

17.1 

7.7 

Too  dark 

14.7 

6.6 

507  A  10 

July         28 

6.71 

60.5 

9.0 

47.7 

i.i 

23.6 

3.5 

507  A  11 

July        31 

16.73 

183.8 

10.9 

144.6 

8.6 

84.5 

5.0 

507  A  12 

August      1 

.81 

5.1 

6.3 

Too  dark 

Trace 

507  A  13 

August      5 

21.22 

254.8 

12.0 

57.3 

2^7 

53.0 

2^4 

507  A  14 

August      7 

17.52 

117.0 

6.6 

325.2 

18.5 

25.5 

1.4 

507  A  15 

August    12 

4.82 

88.2 

18.3 

36.7 

7.6 

25.5 

5.3 

507  A  16 

August    16 

28.79 

105.7 

3.6 

236.2 

8.1 

110.0 

3.8 

507  A  17 

August    17 

4.65 

3.2 

Q.7 

95.4 

20.5 

47.1 

10.1 

507  A  18 

August    20 

8.26 

56.9 

6.8 

90.7 

10.9 

21.6 

2.6 

507  A  19 

Sept.        10 

8.88 

274.1 

30.8 

Too  dark 

106.1 

11.9 

507  A  20 

Sept.       27 

7.70 

28.2 

3.6 

Too  dark 

265.2 

34.4 

507  A  21 

October    3 

18.00 

9.0 

0.5 

Too  dark 

45.1 

2.5 

507  A  22 

October     7 

2.30 

26.8 

11.5 

Too  dark 

5.9 

2.5 

507  A  23 

October  15 

2.40 

10.0 

4.1 

Too  dark 

11.7 

.     4.8 

507  A  24 

October  26 

5.40 

99.0 

18.3 

Too  dark 

23.6 

4.3 

sufficiently  different  in  character  from  the  other  to  render  one  mixture 
more  soluble  and  less  adhesive  than  the  other.  Atmospheric  conditions 
other  than  amount  of  precipitation  may  have  been  responsible  for  the 
recorded  differences,  but  the  necessary  data  for  determination  on  this 
point  are  not  at  hand.  For  a  period  over  82  percent  longer  and  a 
precipitation  of  45  percent  greater  in  1907  than  in  1906  the  natural 
expectation  would  be  the  finding  of  a  proportionately  increased  quan- 
tity of  soluble  copper  in  the  waters  collected  in  the  later  year.  The 
results,  however,  are  directly  opposed  to  this  expectation.  The  quan- 
tity instead  of  being  greater  is  considerably  less.  Apparently  time 


1909] 


BORDEAUX  MIXTURE 


269 


period  and  amount  of  rain  are  not,  in  this  case,  the  important  factors 
in  bringing  copper  into  solution;  that  office  rests  in  other  less  tangible 
factors  that  must  be  isolated,  and  proved  thru  more  extended  investi- 
gations. 

The  chemical  data  obtained  from  the  drip  waters  from  trees  507 
A  and  507  B  appear  in  the  tabulations  pages  268  and  269. 

Chemical  Determinations  from  Waters  Collected  from  Tree  507  B. 


Soluble  constituents 

Serial 

Amount 

Alkalinity  in 

Insoluble 

Number 

Date 

of 

Copper 

terms  of 

copper 

Drip 

calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

Total 

Per  litre 

507  B    1 

June        22 

2.10 

146.3 

69.6 

106.7 

50.8 

404.6 

192.6 

507  B    2 

June        24 

40.75 

352.9 

8.6 

697.0 

17.1 

1125.6 

27.6 

507  B    3 

July           1 

2.50 

28.2" 

11.2 

94.8 

37.9 

27.5 

11.0 

507  B    4 

July           6 

9.49 

79.9 

8.4 

238.1 

25.0 

392.9 

41.4 

507  B    5 

July    9,  10 

25.22 

166.4 

6.5 

132.0 

5.2 

111.9 

4.4 

507  B    6 

July  10,  11 

9.82 

40.9 

4.1 

150.9 

15.3 

35.3 

3.5 

507  B    7 

July  14,  15 

24.10 

95.0 

3.9 

81.6 

3.3 

298.6 

12.3 

507  B    8 

July         17 

6.82 

25.9 

3.7 

324.0 

47.5 

88.4 

12.9 

507  B    9 

July         26 

2.41 

15.9 

6.6 

34.8 

14.4 

53.0 

21.9 

507  B  10 

July         28 

6.83 

40.1 

5.8 

103.2 

15.1 

70.7 

10.3 

507  B  11 

July         31 

16.98 

74.6 

4.3 

258.0 

15.1 

66.4 

3.9 

507  B  12 

August      1 

Lost 

507  B  13 

August      5 

20.28 

56.5 

2.7 

588.1 

29.0 

39.3 

1.9 

507  B  14 

August      7 

17.22 

115.9 

6.7 

66.7 

3.8 

29.4 

1.7 

507  B  15 

August    12 

5.12 

86.7 

16.9 

24.8 

4.8 

25.5 

4.9 

507  B  16 

August    16 

28.93 

40.6 

1.4 

220.6 

7.6 

31.4 

1.0 

507  B  17 

August    17 

4.92 

8.4 

1.7 

56.3 

11.4 

27.5 

5.5 

507  B  18 

August    20 

7.95 

39.0 

4.9 

125.5 

15.7 

39.3 

4.9 

507  B  19 

Sept.        10 

9.11 

66.4 

7.2 

273.3 

30.0 

45.2 

4.9 

507  B  20 

Sept.        27 

7.50 

61.6 

8.2 

Too  dark 

58.9 

7.8 

507  B  21 

October     3 

17.60 

27.1 

1.5 

Too  dark 

17.6 

1.0 

507  B  22 

October     7 

2.40 

1.6 

0.6 

Too  dark 

9.7 

4.0 

507  B  23 

October  15 

2.42 

6.6 

2.7 

Too  dark 

Neutr'l 

8.4 

3.5 

507  B  24 

October  26 

5.03 

29.4 

5.8 

Too  dark 

Neutr'l 

7.8 

1.5 

The  foliage  of  trees  507  A  and  507  B  was  not  injured  to  any  seri- 
ous extent  and  yet  there  were  more  leaves  marked  by  brown  spots  and 
'brown  marginal  areas  than  appeared  on  any  of  the  five  trees  treated 
in  1906.  The  trees  were  sprayed  June  11.  No  injury  followed  im- 
mediately after  spraying,  nor  was  any  observed  for  several  weeks. 
August  12  brown  spots,  few  in  number  and  small  in  size  were  observed 
on  a  few  leaves ;  they  did  not  come  all  at  once,  but  appeared  to  develop 
a  few  at  a  time.  In  making  daily  observations,  it  was  difficult  to  detect 
changes  in  appearance  from  day  to  day,  but  by  September  4  the  spots 
were  numerous  enough  to  attract  attention.  As  the  season  advanced 
and  the  blue  coating  of  Bordeaux  became  somewhat  thin  by  repeated 
washing,  the  spots  became  still  more  conspicuous ;  this  was  largely  the 
result  of  the  distribution  over  the  trees.  A  large  majority  of  the 
leaves  were  uninjured  and  remained  so  to  the  close  of  the  season,  but 
the  few  that  were  injured  were  so  mingled  with  the  perfect  leaves  as  to 


270  BULLETIN  No.   135  [May 

give  the  impression  of  a  greater  amount  of  injury  than  really  existed. 
Why  two  or  three  leaves  among  the  15  or  20  on  a  twig  should  be  in- 
jured, while  all  others  remain  intact,  is  usually  not  answerable  from 
direct  or  even  from  critical  examination.  The  brown  spots  are  not  seen 
to  develop ;  an  examination  one  day  shows  all  leaves  perfect ;  on  next 
examination  spots  are  there.  Possible  causes  can  be  suggested,  but  the 
essential  proof  of  action  of  any  suggested  cause,  is  in  most  cases, 
wanting.  Some  suggested  causes  may  be  disposed  of  by  processes  of 
elimination;  these  are  the  least  complex;  thus,  the  larger  quantity  of 
mixture  deposited  on  leaves  is  eliminated  as  a  cause  of  injury  by  the 
frequent  observation  that  leaves  carrying  very  small  amounts  are  fully 
as  liable  to  injury  as  are  the  more  heavily  coated.  In  like  manner  the 
matters  of  location,  size  of  leaf,  and  certain  atmospheric  conditions 
can  be  dismissed  by  observation,  as  inoperative  factors.  This  narrows 
the  investigation  to  those  less  tangible,  more  obscure  factors  that  in- 
volve nutritive  and  other  organic  functions  of  living  plants.  In  some 
cases  degree  of  injury  appears  to  be  influenced  by  the  health  and  vigor 
of  growth  of  the  plants.  This  is  illustrated  by  the  trees  here  consid- 
ered. Number  507  A  made  a  much  stronger  growth  during  the  season 
than  did  No.  507  B ;  its  general  appearance  indicated  a  degree  of  vital- 
ity not  shown  by  B.  The  number  of  injured  leaves  and  the  extent  of 
injury  on  individuals  was  noticeably  greater  on  507  B  than  on  507  A. 
The  brown  spots  noted  on  these  two  trees  appeared  between  August  12 
and  September  4;  from  this  last  date  on  thru  September  and  Octo- 
ber, no  increase  in  number  or  size  of  spots  could  be  detected.  Why 
development  of  injury  was  confined  to  the  period  named  has  not  been 
determined.  But  it  cannot  be  ascribed  to  any  excess  of  soluble  copper 
present  at  that  particular  time.  The  average  amounts  of  soluble  cop- 
per during  the  period  from  June  11,  the  date  of  spraying,  to  the  ap- 
pearance of  injury,  and  again  for  the  period  from  September  4  to  the 
close  of  the  season  were  both  greater  than  during  the  time  of  develop- 
ment of  injury. 

Yellow  leaves.  During  the  long  interval  between  rains,  August 
20  to  September  10,  a  few  leaves  became  yellow.  Twelve  of  the 
sprayed  leaves  were  thus  affected,  but  as  a  somewhat  greater  number 
of  leaves  on  new  shoots  above,  that  had  not  been  sprayed,  became 
yellow,  at  the  same  time,  yellowing  can  not  have  been  caused  by  any 
direct  action  of  the  spray.  These  yellow  leaves  were  all  carried  down 
by  the  rain  of  September  10  and  there  was  no  further  appearance  of 
yellowing.  When  the  leaves  were  picked  from  the  trees  October  31, 
it  was  noted  that  every  leaf  that  had  been  sprayed  carried  evident  traces 
of  Bordeaux,  and  many  were  still  well  covered. 

COMPARISON  OF  TREES  SUBJECTED  TO  RAIN,  WITH  TREES  SPRAYED 
WITH  CISTERN  WATER 

The  trees  exposed  to  rains  were  the  trees  that  have  been  already 
treated,  namely,  507  A  and  B.  These  were  sprayed  with  the  Bor- 
deaux-Paris green  mixture  June  11  and  subjected  to  24  rains,  giving 
precipitation  of  13.36  inches  during  the  period  of  137  days  ending  with 


1909]  BORDEAUX  MIXTURE  271 

the  last  rain  October  26.  With  these  may  be  compared  two  adjacent 
trees — numbers  607  A  and  607  B — which  were  sprayed  in  exactly  the 
same  manner  on  the  same  day.  Covers  were  provided  to  protect  from 
rain  and  dew,  and  the  two  trees  were  sprayed  at  seven-day  intervals, 
with  cistern  water,  in  amounts  varying  from  6l/2  to  11  litres.  There 
were  18  applications  in  all  between  June  18  and  October  15.  The 
period  between  preliminary  spray  and  the  last  spray  of  rain  water  is 
126  days.  The  waters  collected  from  the  trees  subjected  to  rain  were 
76.069  percent  greater  in  quantity  than  those  from  the  trees  sprayed 
with  water,  and  they  contained  2.38  times  as  much  soluble  copper. 
The  average  amount  of  copper  is  9.06  milligrams  per  litre  for  the  507 
trees,  and  5.17  milligrams  per  litre  for  the  607  trees.  Soluble  copper 
was  present  in  all  waters  from  rains,  and  ranged  in  amount  between 
a  trace  in  the  fourth  water  from  tree  507  A,  to  70  milligrams  per  litre 
in  the  first  water  from  507  B.  Of  the  trees  sprayed  with  cistern  water, 
No.  607  A  yielded  small  amounts  of  soluble  copper  to  every  lot  of 
drip  collected.  The  quantities  varied  from  0.6  milligrams  per  litre  in 
the  water  of  October  1  to  11.1  milligrams  per  litre  in  the  water  of 
September  3.  No.  607  B  yielded  soluble  copper  to  17  of  the  18  lots 
of  water,  in  amounts  between  0.5  milligram  per  litre  and  15.9  milli- 
grams per  litre.  The  seventh  water,  from  the  spray  of  July  30  gave/ 
no  trace  of  soluble  copper.  In  general,  the  amounts  of  copper  in  the 
spray  waters,  applied  at  regular  intervals  in  fairly  uniform  quantities, 
show  much  less  fluctuation  than  do  the  amounts  from  rains  which  were 
widely  variable  in  amount  and  at  very  irregular  intervals.  The  amount 
of  soluble  copper  per  litre  is  much  greater  in  the  waters  from  rains 
than  in  the  spray  waters.  This  is  probably  the  result  of  several  active 
causes;  the  much  greater  quantity  of  water  that  passed  over  the 
leaves ;  the  carbon  dioxide  and  ammonia  carried  by  meteoric  waters ; 
heavy  dews ;  the  greater  mechanical  action  of  falling  rain  drops ;  and, 
in  general,  the  more  complete  exposure  to  atmospheric  conditions. 

The  most  striking  contrast  between  the  two  pairs  of  trees,  is  the 
entire  absence  of  brown  spotting  and  yellowing  of  leaves  on  the  trees 
sprayed  with  water.  There  is  also  a  certain  advantage  in  size  of 
leaves,  an  appearance  of  health  and  sound  vitality  and  an  unusually 
dark  green  color  that  is  all  on  the  side  of  the  foliage  protected  from 
rain  and  sprayed  with  cistern  water.  The  foliage  on  the  507  trees  is 
good,  and,  as  compared  with  unsprayed  leaves,  shows  considerably 
darker  shades  of  green,  but  depth  of  color  is  more  pronounced  in  the 
leaves  of  the  607  trees,  and  this,  in  connection  with  the  absolutely  per- 
fect condition,  gives  the  water  sprayed  trees  a  decided  advantage  when 
compared  with  the  trees  exposed  to  rain.  In  the  matter  of  the  ad- 
hesiveness of  Bordeaux,  the  advantage  is  also  with  the  607  trees.  This 
is  in  great  part  accounted  for  by  the  fact  that  spray  delivered  as  a  fine 
mist,  has  much  less  mechanical  action  in  loosening  and  removing  the 
coating  of  Bordeaux  than  heavier  rain  drops,  especially  when  the  latter 
are  driven  by  wind.  The  607  trees  were  almost  as  intensely  blue  at 
the  time  of  the  last  spraying,  October  15,  as  on  the  day  of  application, 
June  11,  while  the  blue  of  the  507  trees  was  considerably  diminished. 


272 


BULLETIN  No.   135 


[May 


Summarizing  all  the  observations  made  upon  the  trees  under  con- 
sideration, it  is  concluded  that  meteoric  waters  have  the  power  of  con- 
verting the  copper  of  Bordeaux  mixture  into  soluble  forms  at  a  more 
rapid  rate  than  have  waters  applied  as  spray.  This  is  probably  due  to 
the  carbon  dioxide  and  ammonia  contained  in  rains,  but  may  in  part  be 
ascribed  to  differences  in  mechanical  action,  to  heavy  dews  and  more 
complete  exposure  to  the  action  of  the  atmosphere. 

Chemical  Determinations  from  Waters  Collected  from  Trees  607  A  and  607  B. 


Soluble  constituents. 

Serial 
Number 

Date 

Amount 
litres 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

607  A    1 

June        18 

9.56 

30.4 

3.1 

200.2 

20.9 

607  A    2 

June        25 

8.00 

55.3    . 

6.9 

437.9 

54.7 

607  A    3 

July           2 

8.92 

43.6 

4.8 

263.7 

29.5 

607  A    4 

July          9 

9.91 

78.9 

7.9 

272.0 

27.4 

607  A    5 

July         16 

7.58 

46.2 

6.0 

151.0 

19.9 

607  A    6 

July        23 

8.43 

12.9 

1.5 

126.8 

15.0 

607  A    7 

July         30 

6.51 

29.9 

4.5 

118.9 

18.2 

607  A    8 

August      6 

10.36 

46.3 

4.4 

184.0 

17.7 

607  A    9 

August    13 

8.72 

53.0 

6.0 

130.8 

15.0 

607  A  10 

August    20 

7.43 

8.6 

1.1 

235.5 

31.6 

607  A  11 

August    27 

9.23 

12.7 

1.3 

329.5 

35.6 

607  A  12 

Sept.          3 

7.88 

88.0 

11.1 

187.7 

23.8 

607  A  13 

Sept.        10 

8.73 

49.5 

5.6 

641.1 

73.4 

607  A  14 

Sept.        17 

9.62 

44.4 

4.6 

164.0            17.0 

607  A  15 

Sept.        24 

8.73 

21.2 

2.4 

169.1 

19.3 

607  A  16 

October     1 

8.17 

5.1 

0.6 

133.9 

16.3 

607  A  17 

October    8 

9.60 

27.5 

2.8   : 

307.3 

32.0 

607  A  18 

October  15 

11.00 

45.1 

4.1 

221.6 

20.1 

607  B    1 

June        18 

8.56 

5.1 

0.59 

105.2 

12.2 

607  B    2 

June        25 

9.08 

46.8 

5.1 

419.2 

46.1 

607  B    3 

July          2 

7.42 

27.3 

3.6 

234.6 

31.6 

607  B    4 

July           9 

8.33 

126.7 

15.2 

272.0 

32.6 

607  B    5 

July         16 

8.33 

41.3 

4.9 

185.6 

22.2 

607  B    6 

July         23 

7.18 

17.7 

2.4 

150.2 

20.9 

607  B    7 

July         30 

7.53 

None 

96.2 

12.7 

607  B    8 

August      6 

7.61 

32.2 

4^2 

115.8 

15.2 

607  B    9 

August    13 

9.61 

44.7 

4.6 

146.7 

15.2 

607  B  10* 

August    20 

8.09 

32.8 

4.0 

146.0 

18.0 

607  B  11 

August    27 

7.60 

28.3 

3.7 

274  .  7            36  .  1 

607  B  12 

Sept.          3 

7.50 

45.9 

6.1 

180.5 

24.0 

607  B  13 

Sept.        10 

8.37 

133.1 

15.9 

777.2 

92.8 

607  B  14 

Sept.        17 

10.45 

5.9 

0.5 

343.3 

32.8 

607  B  15 

Sept.        24 

9.07 

87.6 

9.6 

87.1 

9.6 

607  B  16 

October     1 

9.13 

134.3 

14.7 

86.4 

9.4 

607  B  17 

October     8 

8.25 

71.6 

8.6 

281.3 

34.0 

607  B  18 

October  15 

7.62 

21.1 

2.7 

103.0 

13.5 

The  entire  absence  of  injury  to  foliage,  of  the  607  trees,  may  be 
in  some  measure  accounted  for  in  the  less  amount  of  soluble  copper 
shown  to  be  present  in  the  waters,  but  it  is  thought  that  at  times  the 
copper  in  solution  was  present  in  sufficient  amount  to  be  injurious, 
had  other  conditions  been  favorable.  The  foliage  of  the  trees  exposed 


1909]  BORDEAUX  MIXTURE  273 

to  rain  is  kept  moist  for  a  much  longer  period  at  the  time  of  each  rain, 
than  is  the  case  with  the  sprayed  trees.  In  spraying,  the  application 
requires  from  5  to  7  minutes  and  within  an  hour  the  foliage  is  dry 
again,  while  the  trees  exposed  to  rain  have  the  leaves  continuously 
wet  for  periods  ranging  from  two  or  three -hours  to  more  than  twenty- 
four  hours. 

Various  experiments  indicate  that  long  continued  moisture  is,  in 
many  cases  a  controlling  factor  in  causing  injury  to  foliage.  But  it 
is  not  operative  in  all  cases ;  hence  there  must  be  other  contributory 
causes,  such  as  condition  of  the  atmosphere,  character  of  the  rain, 
matters  in  solution  in  the  rain  water,  temperature,  and  the  state  of 
vitality  of  the  leaves.  To  isolate  all  possible  agencies  that  may  con- 
tribute to  injurious  action,  test  by  experiment  and  prove  the  connec- 
tion of  each  in  such  manner  as  will  allow  unconditional  conclusions  will 
require  much  more  extended  investigations  than  have  yet  been  made 
in  this  direction.  The  chemical  data  obtained  from  trees  607  A  and 
607  B,  so  far  as  completed,  are  given  in  tabular  form  page  272. 

MAINTAINING  AN  EXCESS  OF  LIME 

For  the  purpose  of  testing  the  effects  of  continuously  maintained 
excess  of  lime  upon  foliage  and  upon  the  solubility  of  the  copper  de- 
posited in  Bordeaux  mixture,  six  trees,  in  three  pairs,  were  used.  The 
trees  were  given  the  numbers  707  A  and  B,  807  A  and  B  and  907  A 
and  B.  Each  tree  was  equipped  with  funnel,  jar  and  other  accessories 
necessary  for  catching  the  drip,  just  as  described  for  other  trees.  Each 
test  is  made  in  duplicate  because  the  average  of  results  from  two  trees 
is  better  basis  for  conclusions  than  results  from  a  single  tree;  one 
serves  as  a  check  upon  the  other.  If  wide  fluctuations  occur  between 
the  results  from  two  trees  that  receive  exactly  the  same  treatment, 
something  is  probably  wrong  with  one  or  the  other;  and  the  cause  of 
the  difference  must  be  traced  out  and  explained.  In  the  experiments 
to  be  described  there  was  remarkable  uniformity  in  the  results  from 
the  two  trees  of  each  pair. 

June  11  the  707  pair  and  the  907  pair  were  heavily  sprayed  with 
the  Bordeaux-Paris  green  mixture  made  after  the  usual  -1  A  ^-50 
formula.  Covers  were  provided  for  the  907  pair  to  protect  the  trees 
from  all  rain  and  dew,  while  the  707  pair  was  left  exposed  to  rains. 
Tree  No.  907  A  with  its  equipment  is  shown  in  Figure  8. 

Commencing  June  18,  seven  days  after  the  application  of  Bor- 
deaux, the  707  trees  were  sprayed  with  milk  of  lime,  4  pounds  to  50 
gallons,  and  this  was  repeated  at  intervals  of  one  week  until  October 
15,  making  a  total  of  18  applications,  in  amounts  averaging  about  8 
litres.  Between  June  22,  the  date  of  first  rain,  and  October  26,  the 
date  of  last  rain,  the  trees  were  washed  by  the  waters  of  24  rains 
giving  a  precipitation  of  13.36  inches.  Adding  the  rains  and  sprays 
we  have  a  total  of  42  lots  of  water  collected  from  each  of  the  two  trees. 
The  gross  amount  of  water  collected  was  a  little  more  than  376  litres 
per  tree,  or  an  average  of  nearly  9  litres  for  each  lot.  The  907  trees, 
those  protected  from  rain,  were  sprayed  with  cistern  water  June  18 


274 


BULLETIN  No.  135 


[May 


one  week  after  the  application  of  Bordeaux.  This  was  repeated  at  in- 
tervals of  one  week  until  October  15,  thus  giving  18  applications,  in 
amounts  averaging  about  8  litres.  June  21  the  same  trees  were  sprayed 
with  milk  of  lime  (4—50)  and  this  was  repeated  at  weekly  intervals 
until  the  number  of  applications  equalled  the  number  given  of  cistern 
'water.  This  brought  the  last  spray  October  18.  The  amounts  at  each 
application  averaged  about  the  same  as  for  the  cistern  water.  From 


Tree    907A,    covered.     Curtain    raised    to    show    drip    jar. 
From   photograph   October    17,    1907. 

each  of  these  trees,  therefore,  36  lots  of  water  were  collected.  The 
gross  amount  of  water  was  a  fraction  less  than  300  litres  per  tree, 
with  an  average  of  8^3  litres  per  lot. 

The  807  pair  of  trees  was  used  solely  to  test  the  action  upon  foli- 
age of  a  continuously  maintained  excess  of  lime  in  connection  with 
free  exposure  to  rain.  The  trees  were  sprayed  with  the  same  milk  of 
lime,  on  the  same  dates,  and  in  approximately  the  same  amounts  as 


1909]  BORDEAUX  MIXTURE  275 

were  applied  on  the  707  trees.  The  only  difference  between  the  two 
pairs  is  that  the  807  pair  received  no  preliminary  spray.  No  Bor- 
deaux was  at  any  time  used  on  these  trees.  The  number  of  waters 
collected,  24  from  rains  and  18  from  sprays,  is  the  same  as  collected 
from  the  707  trees,  and  the  gross  amount  of  water  per  tree  is  approx- 
imately the  same. 

INFLUENCE  OF  LIME  IN  EXCESS  ON  THE  SOLUBILITY  OF  COPPER 

Comparing  the  707  trees  with  the  907  trees  in  the  matter  of  cop- 
per in  solution,  the  most  striking  feature  is  the  irregularity  in  the  ap- 
pearance of  soluble  copper  in  the  waters  from  all  four  trees.  Of  the 
42  waters  collected  from  the  707  trees,  26  from  707  A  and  29  from 
707  B  contain  soluble  copper;  hence  16  from  A  and  13  from  B  were 
free  from  copper.  Of  the  16  lots  from  707  A  that  contain  no  copper, 
12  were  from  milk  of  lime  sprays  and  4  were  from  rains.  Separating 
the  corresponding  copper  free  lots  from  707  B,  gives  8  from  lime 
sprays  and  five  from  rains. 

In  these  waters  containing  copper,  the  amounts  are,  in  general, 
quite  small.  The  maximum  for  707  A  is  56  milligrams  per  litre,  for 
707  B — 33.3  milligrams  per  litre,  both  from  the  second  water  col- 
lected from  a  rain  of  0.1  inch  on  June  22.  The  minimum  is  a  fraction 
of  a  milligram  for  both  trees.  Turning  to  the  covered  trees  it  is  seen 
that  of  the  36  lots  of  water,  13  from  907  A  and  14  from  907  B  con- 
tain copper;  this  leaves  23  lots  from  A  and  22  lots  from  B  that  were 
free  from  copper.  Separating  these  copper  free  lots,  according  to 
the  kind  of  spray,  shows  that  15  of  the  A  lots  and  12  of  the  B  lots 
were  lime  sprays,  while  8  of  the  A  lots  and  10  of -the  B  lots  were  from 
sprays  of  cistern  water.  The  maximum  of  copper  in  milligrams  per 
litre,  is  6.3  in  the  first  water  from  A  and  4.0  in  the  third  water  from  B. 

The  difference  between  the  two  pairs  of  trees  in  amounts  of  sol- 
uble copper,  is  perhaps  best  shown  in  the  averages  of  milligrams  per 
litre,  computed  from  the  waters  containing  copper ;  these  are,  for  the 
707  pair  4.2  milligrams  per  litre  and  for  the  907  pair  1.7  milligrams 
per  litre.  The  averages  in  both  are  low,  but  the  trees  exposed  to  rains 
show  nearly  2l/2  times  as  much<as  the  trees  protected  and  receiving 
water  by  spray  only. 

Combining  the  figures  from  the  two  trees  of  each  pair  and  stating 
the  copper  differences  in  percentages,  it  is  found  that  65.47  percent  of 
the  707  and  only  37.5  percent  of  the  907  waters  contain  soluble  copper. 
Of  the  waters  containing  no  copper  69  percent  of  the  707,  and  60  per- 
cent of  the  907  waters  were  collected  from  lime  sprays.  That  the 
superabundance  of  lime  does  act  in  an  effective  manner  to  check  the 
conversion  of  copper  into  soluble  forms  is  evident  from  the  figures 
given.  It  is  also  evident  that  its  influence  is  most  potent  where 
meteoric  waters  are  excluded.  Comparing  the  trees  sprayed  with  lime 
with  the  507  and  607  pairs  previously  discussed  it  may  be  noted  that 
waters  from  the  507  pair,  which  was  subjected  to  meteoric  waters  only, 
contained  2.15  times  the  number  of  milligrams  of  soluble  copper  per 
litre  as  did  the  waters  from  the  707  pair  which  was  washed  by  the 
same  rains,  but  was  also  given  18  applications  of  milk  of  lime.  Also 


276 


BULLETIN  No.   135 


[May 


that  waters  from  the  607  pair  sprayed  18  times  with  cistern  water, 
yielded  3.04  times  as  many  milligrams  of  soluble  copper  per  litre  as 
was  found  in  the  waters  of  the  907  pair  treated  in  exactly  the  same 

Chemical  Determinations  from  Waters  Collected  from  Tree  707  A. 


Soluble  Constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

707  A    1 

June        18 

6.20 

None 

7118.2 

1148.1 

707  A    2 

June        22 

1.73 

97.0 

56'6 

72.4 

41.8 

707  A    3 

June        24 

36.64 

44.8 

1.2 

1402.3 

38.2 

707  A    4 

June        25 

4.19 

None 

3088.0 

736.9 

707  A    5 

July           1 

2.41 

12.5 

5.1 

222.4 

92.2 

707  A    6 

July           2 

5.30 

None 

5330.8 

1005.8 

707  A    7 

July           6 

10.22 

66.8 

6.5 

618.3              60.5 

707  A    8 

July           9 

8.01 

None 

7976.6 

995.7 

707  A    9 

July    9,  10 

24.76 

17.8 

6^7 

1452  .  1 

58.6 

707  A  10 

July  10,  11 

9.84 

None 

431.1 

43.8 

707  A  11 

July  14,  15 

23.42 

121.0 

5.1 

1223.7 

52.3 

707  A  12 

July         16 

5.55 

15.7 

2.8 

4376.6 

788.5 

707  A  13 

July         17 

7.60 

39.2 

5.1 

603.7 

79.4 

707  A  14 

July         23 

6.76 

93.8 

13.9 

7505.5 

1110.2 

707  A  15 

July         26 

1.96 

21.0 

10.7 

47.8 

24.3 

707  A  16 

July         28 

6.70 

7.4 

1.1 

252.6 

37.7 

707  A  17 

July         30 

8.15 

None 

7851.0 

963.3 

707  A  18 

July        31 

16.31 

78.5 

4!s 

454.8 

27.8 

707  A  19 

August      1 

.72 

Trace 

Trace 

72.7 

100.9 

707  A  20 

August      5 

21.17 

30.5 

1.4 

2430.1 

114.7 

707  A  21 

August      6 

7.22 

None 

9201.3 

1274.3 

707  A  22 

August      7 

17.83 

16.5 

'o'g 

2187.8 

122.7 

707  A  23 

August    12 

4.66 

None 

257.0 

55.1 

707  A  24  . 

August    13 

6.63 

None 

«        .... 

7169.6 

1081.3 

707  A  25 

August    16 

28.59 

29.4 

1.0 

1924.3 

673.0 

707  A  26 

August    17 

4.12 

19.0 

4.6 

323.4 

78.2 

707  A  27 

August    19 

8.15 

28.5 

3.4 

377.1 

46.2 

707  A  28 

August    20 

5.08 

23.3 

4.5 

632Q.O 

1240.0 

707  A  29 

August    27 

5.40 

1.5 

0.2 

7065.9 

1308.8 

707  A  30 

Sept.          3 

3.89 

11.8 

3.0 

4752.4 

1221.7 

707  A  31 

Sept.   9,  10 

5.99 

8.6 

1.4 

Too  dark 

707  A  32 

Sept.        10 

6.93 

None 

7861.5 

1134.4 

707  A  33 

Sept.        17 

5.19 

None 

6452.9 

1243.3 

707  A  34 

Sept.       24 

9.13 

9.0 

V.8 

10598.8 

1160.7 

707  A  35 

Sept.  26,  27 

7.50 

None 

Too  dark 

707  A  36 

October     1 

6.50 

None 

8335.1 

1282.3 

707  A  37  . 

October     3 

16.41 

None 

785.1 

47.8 

707  A  38 

October     7 

2.00 

7.0 

3.5 

65.9 

32.9 

707  A  39 

October     8 

7.10 

None 

7903.3 

1113.1 

707  A  40     !     October  15 

2.07 

6.6 

3.1 

364.1 

175.8 

707  A  41 

October  15 

6.57 

None 

6667.9 

1014.9 

707  A  42 

October  28 

5.18 

97 

i.k 

Too  dark 

manner  except  for  the  weekly  applications  of  milk  of  lime.  The  re- 
sults of  this  test  give  additional  proof  of  the  greater  effectiveness  of 
meteoric  waters  as  compared  with  artificial  spray,  in  converting  the 
copper  of  Bordeaux  mixture  into  soluble  form.  They  also  show  that 


1909] 


BORDEAUX  MIXTURE 


277 


while  lime  in  great  excess  diminished  the  amount,  it  did  not  entirely 
prevent  formation  of  soluble  copper. 

Soluble  copper  and  free  lime,  as  determined  for  the  waters  from 
the  trees  last  considered,  are  given  in  tabular  form  on  pages  276-277 
and  279-280.  Insoluble  constituents  have  not  yet  been  determined. 


Chemical  Determinations  from  Waters  Collected  from  Tree  707  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

707  B    1 

June        18 

6.17 

None 

7254".  3 

1175.6 

707  B    2 

June        22 

2.09 

68.0 

32.5 

78.9 

37.7 

707  B    3 

June        24 

35.71 

162.5 

4.5 

1378.6 

38.6 

707  B    4 

June        27 

6.86 

5.2 

0.7 

6516.1 

949.8 

707  B    5 

July           1 

2.38 

8.6 

3.6 

60.2 

2.52 

707  B    6 

July           2 

7.46 

9.4 

1.2 

5495.5 

736.6 

707  B    7 

July           6 

8.87 

36.6 

4.1 

325.0 

36.6 

707  B    8 

July           9 

6.97 

16.4 

2.3 

6280.0 

901.0 

707  B    9 

July    9,  10 

24.68 

10.3 

0.4 

884.5 

35.8 

707  B  10 

July  10,  11 

10.39 

27.5 

2.6 

472.1 

45.4 

707  B  11 

July  14,  15 

22.40 

15.0 

0.6 

623.9 

27.8 

707  B  12 

July         16 

6.52 

3.2 

0.4 

6353.6 

974.4 

707  B  13 

July         17 

7.15 

12.0 

1.6 

536.7 

75.0 

707  B  14 

July         23 

7.26 

4.8 

0.6 

7998.6 

1101.7 

707  B  15 

July         26 

2.27 

3.4 

1.4 

87.4 

38.5 

707  B  16 

July        28 

6.47 

6.6 

1.0 

161.6 

24.9 

707  B  17 

July         30 

7.22 

5.9 

0.8 

6943.1 

961.6 

707  B  18 

July    '    31 

16.32 

37.7 

2.3 

429.2 

26.3 

707  B  19 

August      1 

.93 

None 

41.7 

44.8 

707  B  20 

August      5 

19.68 

11.8 

6^6 

581.4 

29.5 

707  B  21 

August      6 

5.78 

None 

7222.9 

1249.4 

707  B  22 

August      7 

16.34 

10.4 

0.6 

879.3 

53.8 

707  B  23 

August    12 

4.88 

23.3 

4.7 

273.4 

56.0 

707  B  24 

August    13 

6.07 

None 

6451.7 

1062.8 

707  B  25 

August    16 

28.16 

37.7 

1^3 

1104.3 

39.2 

707  B  26 

August    17 

4.55 

None 

296.7 

65.2 

707  B  27 

August    19 

7.79 

10.6 

1.3 

465.8 

59.7 

707  B  28 

August    20 

5.14 

None 

6270.8 

1220.0 

707  B  29 

August    27 

5.45 

2.5 

OA 

6908.8 

1267.5 

707  B  30 

Sept.          3 

5.38 

2.6 

0.4 

6437.8 

1196.4 

707  B  31 

Sept.  9,  10 

5.63 

3.4 

0.6 

Too  dark 

707  B  32 

Sept.        10 

8.19 

None 

5992.9 

731.7 

707  B  33 

Sept.        17 

6.20 

3.1 

0.5 

3044.2 

491.0 

707  B  34 

Sept.        24 

6.20 

None 

7222.9 

1165.0 

707  B  35 

Sept.  26,  27 

6.94 

None 

497.2 

71.6 

707  B  36 

October     1 

6.20 

6.1 

0.9 

7693.9 

1240.9 

707  B  37 

October     3 

15.55 

9.8 

0.6 

821.7 

52.8 

707  B  38 

October     7 

2.10 

2.3 

1.0 

71.0 

33.8 

707  B  39 

October     8 

3  .  55            None 

4671.6 

1315.9 

707  B  40 

October  15 

3.10 

Nnnp 

Too  dark 

707  B  41 

October  15 

7  .  76             None 

8216.4 

1058.8 

707  B  42 

October  26 

4.71             None 

Too  dark 

278  BULLETIN  No.   135  [May 

CONDITION  OF  FOLIAGE  OF  TREES  SPRAYED  WITH  LIME 

Foliage  of  the  707  trees  was  in  excellent  condition  thruout  the 
season.  The  first  spray  of  milk  of  lime  obscured  the  blue  color  of  the 
Bordeaux  and  gave  a  white  coating  which  was  still  retained  when  the 
leaves  were  picked  October  31.  Both  trees  made  a  vigorous  growth, 
the  new  shoots  finally  overtopping  the  funnel  by  two  feet  or  more. 
About  the  middle  of  July  the  large  size  of  the  individual  leaves  of 
these  trees  attracted  attention  and  comparisons  were  made  with  leaves 
from  adjacent  trees  of  the  same  variety  that  had  not  been  sprayed. 
The  sprayed  leaves  were  evidently  larger.  This  observation  was  re- 
peated several  times  at  intervals  during  the  following  months  and  the 
comparison  was  extended  to  include  all  the  trees  sprayed  with  lime, 
the  507  trees  sprayed  with  Bordeaux  only,  as  well  as  trees  that  had 
not  been  sprayed.  The  six  trees  receiving  applications  of  lime  shared 
the  advantage  in  the  matter  of  size.  From  all  of  them  the  leaves 
averaged  distinctly  larger  than  leaves  from  the  other  .trees.  No  dif- 
ference could  be  detected  between  leaves  from  the  trees  sprayed  with 
Bordeaux  mixture  and  milk  of  lime,  and  those  sprayed  only  with 
milk  of  lime.  The  aggregate  of  observations  suggests  a  stimulating 
action  on  the  part  of  the  lime,  that  had  operated  in  the  direction  of 
increase  in  size ;  whether  by  direct  action  upon  the  leaves,  or  by  reason 
of  the  protective  covering  afforded,  is  not  apparent.  Tt  is  hoped  that 
further  investigation  of  the  action  here  involved  can  be  undertaken 
during  the  present  season. 

Observations  and  comparisons  were  also  made  at  frequent  inter- 
vals upon  the  color  of  leaves.  These  gave  very  uniform  results  which 
lead  to  the  conclusion  that  Bordeaux  mixture  has  a  decided  influence 
upon  color.  Under  a  coating  of  Bordeaux  the  leaf  becomes  much 
deeper  green  and  this  darker  color  is  retained  even  after  the  coating 
is  mostly  washed  away.  Contrasted  with  leaves  of  equal  age  and 
similar  location  that  had  not  been  sprayed  with  Bordeaux  the  differ- 
ence is  very  striking.  Leaves  coated  with  lime  only  become  some- 
what darker  than  leaves  not  treated,  but  the  shade  of  green  is  not  so 
deep  as  is  assumed  under  a  coating  of  Bordeaux. 

No  burning  or  other  injury  to  foliage  was  observed  on  the  707 
trees  until  September  4;  on  that  date,  a  few  brown  marginal  spots 
were  discovered  on  some  of  the  lower  leaves.  The  number  of  these 
spots  did  not  appear  to  increase,  and  individual  spots  remained  small, 
as  when  first  discovered.  Notes  taken  October  19th  say — '"Very  few 
brown  spots.  A  few  of  the  lower  leaves  have  each  from  1  to  3  small 
brown  marginal  areas,  but  the  injury  is  insignificant." 

The  807  trees  sprayed  with  milk  of  lime  only,  remained  entirely 
free  from  brown  spots  or  burned  margins  thruout  the  season.  The 
experience  with  these  trees  shows  that  lime  alone  has  little  adhesive- 
ness; the  trees  are  white  immediately  after  spraying,  but  the  coating 
scales  off  quite  readily  and  each  rain  removed  nearly  all  that  remained. 
Comparison  with  the  707  trees,  indicates  that  the  Bordeaux  acts  as  a 
binder,  that  holds  the  lime  upon  the  leaves  for  some  time.  The  907 


1909] 


BORDEAUX  MIXTURE 


279 


trees  protected  from  rain  and  sprayed  alternately  with  lime  and  cis- 
tern water,  retained  the  leaves  in  perfect  condition  to  the  end  of  the 
season. 

Yellow  leaves:     During  the  examination  of  the  707  trees  on  Sep- 
tember 4,  it  was  observed  that  a  few  leaves  scattered  over  the  trees 

Chemical  Determinations  from  Waters  Collected  from  Tree  907  A. 


Serial 
Number 

Date 

Amount 
of 
drip 

Soluble  constituents 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

907  A    1 

June        18 

6.10 

38.8 

6.3 

202.6 

33.2 

907  A    2 

June        21 

3.64 

6.6 

1.8 

4187.2 

1150.3 

907  A    3 

June        25 

10.90 

43.2 

3.9 

447.5 

41.0 

907  A    4 

June        28 

5.91 

None 

5835.9 

987.4 

907  A    5 

July          5 

7.56 

9.4 

i.2 

549.6 

72.7 

907  A    6 

July          5 

7.68 

None 

7144.4 

930.2 

907  A    7 

July          9 

10.93 

4.7 

6!i 

293.1 

26.8 

907  A    8 

July         12 

5.71 

None 

6620.0 

1159.4 

907  A    9 

July         16 

9.81 

46.4 

4.7 

274.6 

28.0 

907  A  10 

July         19 

8.92 

None 

7981.8 

894.8 

907  A  11 

July         23 

7.19 

11.7 

l.Q 

361.7 

50.3 

907  A  12 

July        26 

6.97 

10.3 

1.3 

7181.0 

1030.2 

907  A  13 

July        30 

5.46 

None 

250.4 

45.8 

907  A  14 

August      2 

6.19 

None 

6673.3 

1078.0 

907  A  15 

August      6 

10.65 

None 

497.8 

46.7 

907  A  16 

•  August      9 

8.39 

None 

10041.4 

1196.7 

907  A  17 

August    13 

7.95 

None 

272.1 

34.2 

907  A  18 

August    16 

8.38 

None 

10598.8 

1264.7 

907  A  19 

August    20 

8.70 

8.6 

6.9 

674.4 

77.5 

907  A  20 

August    23 

9.29 

None 

11786.9 

1268.7 

907  A  21 

August    27 

9.70 

None 

669.4 

69.0 

907  A  22 

August    30 

9.33 

13.6 

1*4 

11549.3 

1237.8 

907  A  23 

Sept.          3 

11.48 

5.4 

0.4 

523.4 

45.5 

907  A  24 

Sept.         6 

6.75 

None 

8565.4 

1268.8 

907  A  25 

Sept.        10 

8.70 

1.9 

0.2 

455.3 

52.3 

907  A  26 

Sept.        13 

7.90 

None 

9709.0 

1229.0 

907  A  27 

Sept.        17 

9.01 

None 

376.8 

41.8 

907  A  28 

Sept.       20 

7.11 

None 

9342.7 

1313.9 

.607  A  29 

Sept.       24 

11.27 

9.7 

0.8 

259.1 

22.9 

907  A  30 

Sept.        27 

8.30 

None 

10446  .  1 

1258.5 

907  A  31 

October     1 

7.77 

None 

212.7 

27.4 

907  A  32 

October    4 

9.09 

None 

10337.1 

1137.1 

907  A  33 

October    8 

8.27 

None 

223.0 

26.9 

907  A  34 

October  11 

8.05 

None 

9106.1 

1131.1 

907  A  35 

October  15 

7.40 

None 

314.0 

42.4 

907  A  36 

October  18 

10.04 

None 

11136.0 

1109.1 

were  in  part  yellow  or  had  assumed  the  light  greenish  yellow  color 
that  precedes  complete  yellowing.  These  leaves  became  entirely  yel- 
low and  fell  with  the  rain  the  evening  of  September  9.  There  were 
14  from  707  A  and  20  from  707  B.  At  this  same  time,  leaves  in  about 
the  same  numbers  became  yellow  and  fell  from  the  807  trees.  Similar 
yellowing  occurred  on  the  507  trees,  as  has  already  been  mentioned. 
The  yellowing  on  the  807  trees,  which  received  no  Bordeaux,  occur- 


280 


BULLETIN  No.   135 


[May 


ring  coincident  with  that  on  the  other  trees  referred  to,  and  also  on 
many  trees  that  had  not  been  sprayed,  indicated  some  cause  other  than 
Bordeaux.  A  sufficient  number  of  trees  were  affected  with  yellowing 
concurrently,  to  give  the  appearance  of  an  epidemic,  altho  a  very  mild 
one.  The  cause  is  not  known,  but  may  lie  in  some  atmospheric  or  soil 
condition.  It  is  significant  that  the  907  trees  did  not,  at  this,  or  any 
other  time  during  the  season,  show  a  single  yellow  leaf. 

Chemical  Determinations  from  Waters  Collected  from  Tree  907  B. 


Serial 
number 

Date 

Amount 
of 
drip 

Soluble  constituents 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total  . 

Per  litre 

907  B    1 

June        18 

7.69 

None 

214.7 

27.9 

907  B    2 

June        21 

4.62 

11.7 

2^5 

5443.3 

1178.2 

907  B    3 

June        25 

10.42 

'  42.6 

4.0 

471.5 

45.2 

907  B    4 

June        28 

7.76 

None 

7461.7 

957.8 

907  B    5 

July           2 

10.22 

30.2 

2.9 

783.4 

76.6 

907  B    6 

July           5 

9.68 

3.2 

0.3 

9185.6 

948.9 

907  B    7 

July           9 

9.51 

4.2 

0.4 

276.4 

29.0 

907  B    8 

July         12 

9.94 

None 

8923.9 

897.7 

907  B    9 

July         16 

10.90 

15.7 

'i!4 

494.6 

45.3 

907  B  10 

July         19 

7.03 

9.8 

1.3 

7327.6 

1042.3 

907  B  11 

July         23 

8.22 

None 

357.3 

43.4 

907  B  12 

July         26 

9.94 

8.0 

0.8 

10596.2 

1066.0 

907  B  13 

July         30 

8.77 

23.2 

2.6 

794.1 

90.5 

907  B  14 

August      2 

9.75 

None 

10331.9 

1059.6 

907  B  15 

August      6 

10.11 

None 

481.7 

47.6 

907  B  16 

August      9 

8.88 

None 

10468.0 

1178.8 

907  B  17 

August    13 

7.69 

None 

186.7 

24.2 

907  B  18 

August    16 

9.15 

None 

11373.5 

1243.0 

907  B  19 

August    20 

9.50 

6.1 

'6!e 

720.9 

75.8 

907  B  20 

August    23 

6.96 

2.9 

0.4 

9002.5 

1293:5 

907  B  21 

August    27 

7.53 

3.1 

0.4 

548.1 

72.7 

907  B  22 

August    30 

6.10 

4.2 

0.7 

7502.9 

1229.8 

907  B  23 

Sept.          3 

6.75 

10.8 

1.6 

405.6 

60.0 

907  B  24 

Sept.          6 

8.53 

None 

10788.2 

1264.7 

907  B  25 

Sept.        10 

7.00 

None 

385.6 

55.0 

907  B  26 

Sept.        13 

7.12 

None 

8793  .  1 

1234.9. 

'  907  B  27 

Sept.        17 

13.18 

None 

381.8 

28.9 

907  B  28 

Sept.       20 

9.46 

None 

12509.6 

1322.3 

907  B  29     1     Sept.        24 

7.95 

None 

209.3 

26.3 

907  B  30         Sept.        27 

8.27 

None 

9375.2 

1133.6 

907  B  31 

October     1 

8.30 

None 

210.7 

25.3 

907  B  32 

October     4 

6.71 

None 

7327.6 

1092.0 

907  B  33         October     8 

7.85 

None 

162.7 

20.7 

907  B  34         October  11 

7.40 

None 

7567.8 

1022.6 

907  B  35         October  15 

7.50 

None 

261.7 

34.8 

907  B  36     1     October  18 

6.23 

None 

5888.7 

945.2 

FURTHER  TRIAL  OF  THE  BORDEAUX-ARSENATE  OF  LEAD  COMBINATION 

Two  trees  were  sprayed  with  Bordeaux  arsenate  of  lead  combina- 
tion made  after  the  same  formula  and  applied  in  the  same  manner,  as 
to  tree  No.  49  in  1906.  The  spraying  was  done  June  21,  and,  in  the 
127  days  between  that  date  and  October  26,  the  trees  received  the 


1909] 


BORDEAUX  MIXTURE 


281 


Chemical  Determinations  from  Waters  Collected  from  Trees  1907  A  and  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1907  A    1 

June        22 

1.99 

29.6 

14.8 

78.9 

39.6 

1907  A    2 

June        24 

42.05 

57.9 

1.3 

1104.6 

26.2 

1907  A    3 

July          1 

2.43 

11.0 

4.5 

54.4 

22.3 

1907  A    4 

July         '  6 

9.50 

31.4 

3.3 

428.1 

45.0 

1907  A    5 

July    9,  10 

25.43 

88.5 

3.4 

267.4 

10.5 

1907  A    6 

July  10,  11 

11.04 

40.0 

3.6 

132.4 

12.0 

1907  A    7 

July  14,  15 

23.55 

90.7 

3.8 

178.4 

7.5 

1907  A    8 

July         17 

6.75 

88.3 

13.0 

84.2 

12.4 

1907  A    9 

July        26 

2.54 

11.5 

4.5 

70.9 

27.9 

1907  A  10 

July         28 

6.72 

73.1 

10.8 

71.7 

10.6 

1907  A  11 

July         31 

17.13 

121.0 

7.0 

131.4 

7.6 

1907  A  12 

August      1 

1.23 

16.8 

13.6 

34.1 

27.7 

1907  A  13 

August      5 

20.60 

95.0 

4/6 

188.6 

9.1 

1907  A  14 

August      7 

17.60 

60.5 

3.4 

193.4 

10.9 

1907  A  15 

August    12 

5.32 

34.5 

6.5 

42.9 

8.0 

1907  A  16 

August    16 

29.00 

49.9 

1.7 

183.1 

6.3 

1907  A  17 

August    1  7 

4.89 

.      8.9 

1.8 

46.8 

9.4 

1907  A  18 

August    19 

8.19 

37.7 

4.6 

111.4 

13.6 

1907  A  19 

Sept.   9,  10 

9.42 

82.1 

8.7 

334.4 

35.4 

1907  A  20 

Sept.       27 

7.87 

79.3 

10.0 

Too  dark 

1907  A  21 

October     3 

18.38 

7.8 

0.4 

143.9 

7.8 

1907  A  22 

October     7 

2.70 

14.9 

5.5 

Too  dark 

1907  A  23 

October  15 

2.48 

None 

Too  dark 

1907  A  24 

October  26 

5.34 

35.4 

e'e 

Too  dark 

1907  B    1 

June        22 

2.05 

21.4 

10.4 

81.6 

39.8 

1907  B    2 

June        24 

40.90 

139.8 

3.4 

935.3 

22.8 

1907  B    3 

July           1 

2.38 

1.7 

0.6 

73.0 

30.6 

1907  B    4 

July          6 

9.13 

61.8 

6.7 

171.4 

18.7 

1907  B    5 

July    9,  10 

25.44 

73.4 

2.8 

153.1 

6.0 

1907  B    6 

July  10,  11 

10.71 

19.6 

1.8 

94.9 

8.8 

1907  B    7 

July  14,  15 

22.56 

67.6 

2.9 

82.4 

3.6 

1907  B    8 

July         17 

6.66 

76.1 

11.4 

52.0 

7.8 

1907  B    9 

July         26 

2.63 

1.7 

0.6 

20.4 

7.7 

1907  B  10 

July         28 

6.60 

70.2 

10.6 

46.6 

7.0 

1907  B  11 

July        31 

16.08 

153.6 

8.3 

79.5 

4.9 

1907  B  12 

August      1 

1.18 

33.1 

28.0 

22.1 

18.7 

1907  B  13 

August      5 

19.90 

62.7 

3.1 

182.1 

9.1 

1907  B  14 

August      7 

16.30 

65.6 

4.0 

127.3 

7.8 

1907  B  15 

August    12 

5.17 

71.2 

13.7 

37.6 

7.2 

1907  B  16 

August    16 

28.05 

67.4 

2.4 

109.9 

3.9 

1907  B  17 

August    17 

4.82 

15.0 

3.1 

43.6 

9.0 

1907  B  18 

August    19 

7  -.82 

11.8 

1.5 

173.6 

22.2 

1907  B  19 

Sept.   9,  10 

7.82 

82.5 

10.5 

Too  dark 

1907  B  20 

Sept.       27 

7.73 

55.0 

7.1 

Too  dark 

1907  B  21 

October     3 

17.69 

8.8 

0.5 

Too  dark 

1907  B  22 

October     7 

2.50 

None 

Too  dark 

1907  B  23 

October  15 

2.40 

None 

Too  dark 

1907  B  24 

October  26 

5.11 

13.4 

2^6 

Too  dark 

282  BULLETIN  No.   135  [May 

waters  of  24  rains.  The  average  amount  of  drip  collected  was  11.5 
litres.  Of  the  48  lots  from  the  two  trees,  all  but  three  contained  solu- 
ble copper  in  measurable  quantity.  The  maximum  per  litre  was  28.0 
milligrams ;  the  average  for  the  two  trees  6.4  milligrams  per  litre.  The 
essential  differences  between  these  trees  and  tree  No.  49  of  1906  are 
that  the  trees  of  1907  were  under  test  for  three  times  as  long,  were 
washed  by  more  than  twice  the  number  of  rains,  and  the  quantities  of 
water  were  nearly  twice  as  large.  The  quantities  of  soluble  copper 
were,  however,  greater  in  1906  than  in  1907.  The  maximum  per 
litre  was  3^  times  greater  in  1906.  The  averages  were  24.2  milli- 
grams per  litre  in  1906,  and  6.4  milligrams  per  litre  in  1907.  The  an- 
omally  in  this  test  lies  in  the  effect  upon  foliage.  In  1906  there  was 
no  injury  to  foliage;  in  1907  contrary  to  expectations,  the  leaves  of 
both  trees  were  conspicuously  marked  by  brown  spots  and  burned 
marginal  areas.  By  no  means  all  leaves  were  injured,  many  remained 
perfect,  but  the  number  affected  was  sufficient  to  class  the  injury  as 
serious.  Brown  spots  did  not  appear  immediately  after  spraying. 
For  a  long  time  the  leaves  were  without  blemish.  Brown  spots  first 
•appeared  at  the  same  time  that  similar  injury  appeared  on  the  leaves 
of  the  507  trees  sprayed  with  the  Bordeaux  Paris  green  mixture.  The 
spots  were  more  numerous,  individual  spots  were  larger  and  increase 
in  number  continued  longer  than  was  the  case  with  the  507  trees.  All 
circumstances,  in  any  way  connected  with  these  tests,  have  been 
carefully  canvassed,  in  the  effort  to  determine  the  cause  of  injury  in 
this  particular  case,  but  thus  far  it  has  been  found  impossible  to  iso- 
late all  the  possible  factors,  or  to  secure  that  degree  of  proof  necessary 
as  a  basis  for  definite  conclusions.  The  injuries  inflicted  are  identical 
in  character  with  injuries  produced  by  copper  sulphate  solutions,  and 
it  is  believed  and  assumed  that  copper  in  solution  was  the  active  agent 
responsible  for  the  burning.  The  problem  is— why  was  serious  injury 
inflicted  when  the  copper  in  solution  averaged  only  6.4  milligrams  per 
litre,  while  in  the  year  previous  with  an  average  of  copper  in  solution 
almost  four  times  as  large,  the  leaves  suffered  no  injury?  Apparently, 
ability  to  do  injury  does  not  depend  upon  the  amount  of  copper  in  so- 
lution. That  the  cause  of  injury  was  not  strictly  local, — confined  in 
operation  to  the  two  trees  under  consideration, — is  shown  in  the  con- 
current appearance  of  injury  of  the  same  nature  on  the  507  and  some 
other  trees.  The  fact  of  injury,  at  a  particular  time,  to  all  trees 
sprayed  with  Bordeaux  mixture  except  those  protected  from  meteoric 
waters,  points,  as  in  a  case  previously  recorded,  to  some  power  inher- 
ent in  falling  rain,  or  to  some  particular  state  of  the  atmosphere  at  the 
time  that  may  act  directly,  or  indirectly,  by  inducing  a  condition  of 
susceptibility  in  the  trees.  Results  from  these  two  trees  are  tabulated 
on  page  281. 

ACTION  OF  CARBONATED  WATER 

To  test  the  action  of  carbon  dioxide  as  an  agent  influencing  the 
solubility  of  copper  deposited  on  the  leaves  in  Bordeaux  mixture,  four 
trees  were  used.  These  trees  were  equipped  alike,  were  given  the  same 
preliminary  spray  of  standard  Bordeaux-Paris  green  mixture,  and 


1909]  BORDEAUX  MIXTUR*.  283 

were  provided  with  covers  to  protect  from  rain.  One  pair  received 
the  three  applications  of  Bordeaux  June  11,  and  between  June  18  and 
October  15  was  given  18  applications  at  intervals  of  one  week,  of  dis- 
tilled water  thru  which  a  stream  of  carbon  dioxide  had  been  allowed 
to  pass  for  from  15  to  18  hours.  The  other  pair  received  the  prelim- 
inary spray  of  Bordeaux  June  17  and,  between  June  25  and  October 
15,  was  sprayed  17  times,  at  weekly  intervals  with  distilled  water.  The 
results  from  the  two  trees  of  each  pair  are  closely  approximate.  Dis- 
tilled water  was  used  a  little  more  freely  than  was  the  carbonated 
water  and  in  consequence  the  average  quantity  at  each  application  was 
9.6  litres  while  the  average  for  the  carbonated  waters  was  6.6  litres. 
Soluble  copper  was  present  in  all  waters  from  the  trees  sprayed  with 
carbonated  water  and  in  15  of  the  17  lots  collected  from  the  trees 
sprayed  with  distilled  water.  The  average  maximum  of  copper  in 
solution  was  25.9  milligrams  per  litre  for  the  carbonated  waters  and 
13.2  milligrams  per  litre  for  the  distilled  waters;  the  average  minimum 
was  0.9  milligram  per  litre  for  the  carbonated ;  0.45  milligram  per  litre 
for  the  distilled  waters.  Considering  all  waters  from  each  pair,  the 
average  was  8.2  milligrams  per  litre  for  the  carbonated  and  4.4  milli- 
grams per  litre  for  the  distilled.  The  averages  show  very  nearly 
double  the  amount  of  copper  in  solution  in  the  carbonated  waters,  and 
these  results,  as  far  as  they  go,  confirm  the  generally  accepted  opinion 
that  carbon  dioxide  is  an  active  agent  in  converting  the  copper  of  Bor- 
deaux into  soluble  forms.  The  foliage  of  these  four  trees  remained 
in  perfect  condition  thru  the  season ;  no  brown  spots  could  be  detected, 
and  there  was  no  yellowing  of  leaves.  This  absence  of  injury  as  in 
the  case  of  other  covered  trees,  indicates  one  of  two  things ;  either  the 
amount  of  copper  in  solution  is  too  small  to  be  injurious,  or  there  is 
some  agency  other  than  copper  brought  into  solution  thru  the  action  of 
carbon  dioxide,  and  from  which  these  trees  were  defended  by  the 
covers,  that  is  the  cause,  or  at  least,  one  of  the  causes  of  injury  to  the 
foliage  of  apple  trees  sprayed  with  Bordeaux  mixture.  The  average 
amounts  of  copper  shown  to  be  in  solution  are  small,  but  there  were 
periods  when  quantities  approaching  the  maximum  found  in  the  waters 
from  the  trees  sprayed  with  carbonated  water  were  present,  and  these 
amounts  approximate  the  amounts  known  to  be  present  in  waters  from 
other  trees  that  did  suffer  injury.* 

A  further  test  of  the  influence  of  carbonated  water  may  be  re- 
corded here.  Two  pairs  of  trees  were  sprayed  alike  June  17  with  a 
Bordeaux  Paris  green  mixture,  made  with  a  greatly  reduced  quantity 
of  lime.  The  formula  used  was  4-1-^-50.  One  pair  of  the  trees 
was  provided  with  covers  to  protect  from  rain,  and  was  sprayed  once 
each  week,  from  June  25  to  October  15,  with  carbonated  water,  in 
amounts  that  averaged  6.31  litres  for  each  application.  The  number 
of  applications  was  17.  The  companion  pair  was  left  exposed,  and, 
•between  June  22  and  October  26,  was  subjected  to  24  rains,  which 
gave  an  average  of  10.9  litres  of  water  for  each  lot  of  drip  collected. 

'Determinations  from  the  waters  from  trees  1007  A  and  B,  sprayed  with  carbonated  water, 
and  from  trees  1307  A  and  B,  sprayed  with  distilled  water,  are  given  in  tabular  form  on 
pages  284  and  285. 


284 


BULLETIN  No.   135 


[May 


Copper  in  solution  was  found,  in  measurable  quantities,  in  all 
waters  from  each  of  the  four  trees.  The  amounts  in  the  rain  waters 
show  greater  fluctuations  than  do  those  in  the  carbonated  waters,  but 
the  averages  are  not  widely  separated.  The  maxima  for  the  trees  ex- 
posed to  rains  are  51.2  and  146.9  milligrams  per  litre;  for  the  two 
trees  sprayed  with  carbonated  water  53.9  milligrams  and  68.5  milli- 
grams per  litre.  The  average  minimum  is  1.4  milligrams  per  litre  for 
the  rain  waters  and  4.5  milligrams  per  litre  for  the  carbonated  waters. 

Chemical  Determinations  from  Waters  Collected  from  Trees  1007  A  and  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1007  A    1 

June        18 

7.41 

5.1 

0.6 

160.6 

21.6 

1007  A    2 

June        25 

5.99 

218.8 

36.5 

329.7 

55.0 

1007  A    3 

July           2 

5.38 

31.4 

5.8 

132.9 

24.7 

1007  A    4 

July           9 

6.16 

42.4 

6.8 

147.8 

23.9 

1007  A    5 

July         16 

6.72 

54.0 

8.0 

435.7 

64.8 

1007  A    6 

July         23 

6.45 

55.7 

8.6 

261.9 

40.6 

1007  A    7 

July        30 

6.80 

11.0 

1.6 

113.9 

16.7 

1007  A    8 

August      6 

6.85 

29.3 

4.2 

329.4 

48.0 

1007  A    9 

August    13 

5.77 

31.1 

5.3 

87.1 

15.0 

1007  A  10 

August    20 

7.15 

40.4 

5.6 

272.2 

38.0 

1007  A  11 

August    27 

6.66 

66.9 

10.0 

290.5 

43.6 

1007  A  12 

Sept.         3 

6.45 

54.0 

8.3 

181.3 

28.1 

1007  A  13 

Sept.        10 

6.40 

64.8 

10.1 

134.0 

20.9 

1007  A  14  i     Sept.        17 

6.32 

60.1 

9.5 

104.7 

16.5 

1007  A  15  j     Sept.       24 

6.55 

55.0 

8.3 

97.1 

14.8 

1007  A  16 

Sept. 

6.00 

61.0 

10.1 

Too  dark 

1007  A  17 

October     8 

7.00 

39.3 

5.6 

67.0 

'^'.5 

1007  A  18 

October  15 

6.72 

20.6 

3.0 

64.0 

9.5 

1007  B    1 

June       18 

8.53 

9.4 

1.1 

184.1 

21.5 

1007  B    2 

June       25 

5.97 

92.4 

15.4 

305.1 

51.1 

1007  B     3 

July          2 

3.05 

17.5 

5.7 

62.0 

20.3 

1007  B     4 

July          9 

7.23 

43.2 

5.9 

212.3 

29.3 

1007  B     5 

July        16 

9.97 

110.0 

11.0 

105.5 

10.5 

1007  B     6 

July        23 

6.57 

82.5 

12.5 

123.5 

18.7 

1007  B    7 

July        30 

6.83 

62.5 

9.1 

127.1 

18.6 

1007  B     8 

August     6 

7.14 

54.0 

7.5 

416.1 

58.2 

1007  B     9 

August  13 

6.32 

32.3 

5.1 

66.6 

10.5 

1007  B  10 

August  20 

7.35 

45.1 

6.1 

141.8 

19.2 

1007  B  11 

August  27 

6.90 

54.0 

7.8 

226.0 

32.7 

1007  B  12 

Sept.         3 

6.98" 

54.2 

7.7 

234.3 

33.5 

1007  B  13 

Sept.       10 

6.55 

22.0 

3.3 

238.1 

36.3 

1007  B  14 

Sept.       17 

6.32, 

100.9 

15.9 

131.6 

20.8 

1007  B  15 

Sept.       24 

6.55 

86.4 

13.1 

176.1 

26.8 

1007  B  16 

October    1 

6.00 

80.0 

13.3 

Too  dark 

1007  B  17 

October    8 

7.00 

35.4 

5.0 

89.7 

\2.8 

1007  B  18 

October  15 

6.82 

20.2 

2.0 

77.4 

11.3 

The  averages  of  all  waters  give   15.6  milligrams  per  litre   for  rain 
waters  and  17.4  milligrams,  per  litre  for  carbonated  waters. 

It  may  be  concluded  from  this  test  that  carbonated  water  has 
about  the  same  solvent  action  upon  the  copper  of  Bordeaux  as  has  rain 
water.  The  carbonated  water  acts  with  greater  uniformity,  and  at  no 


1909] 


BORDEAUX  MIXTURE 


285 


time  acts  with  sufficient  vigor  to  bring  excessive  amounts  into  solu- 
tion. Comparing  the  amounts  from  these  trees  with  the  amounts  from 
the  trees  sprayed  with  standard  mixture  and  treated  in  like  manner 
with  carbonated  water,  it  is  apparent  that  reduction  in  lime  has  in- 
creased the  amount  of  copper  in  solution  by  more  than  100  percent. 
The  amount  of  lime  used,  in  the  mixtures  applied  to  these  trees,  is 

Chemical  Determinations  from  Waters  Collected  from  Trees  1307  A  and  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1307  A    1 

June        25 

6.96 

73.5 

10.5 

380.6 

54.6 

1307  A    2 

July           2 

7.98 

12.9 

1.6 

269.5 

33.7 

1307  A    3 

July           9 

9.22 

9.4 

1.0 

312.9 

33.9 

1307  A    4 

July         16 

11.73 

6.0 

0.5 

349.6 

29.8 

1307  A    5 

July         23 

9.98 

69.5 

6.9 

138.6 

13.8 

1307  A    6 

July         30 

11.10 

23.5 

2.1 

159.6 

14.3 

1307  A    7 

August      6 

11.63 

83.8 

7.2 

158.6 

13.6 

1307  A    8 

August    13 

10.34 

41.1 

3.9 

124.6 

12.0 

1307  A    9 

August    20 

11.10 

22.0 

1.9 

281.6 

25.3 

1307  A  10 

August    27 

9.58 

27.6 

2.8 

456.1 

47.6 

1307  A  11 

Sept.          3 

9.38 

35.0 

3.7 

198.1 

21.1 

1307  A  12 

Sept.        10 

6.81 

37.3 

5.4 

145.9 

21.4 

1307  A  13 

Sept.        17 

8.81 

34.5 

3.9 

25.2 

2.8 

1307  A  14 

Sept.        24 

9.80 

28.2 

2.8 

130.6 

13.3 

1307  A  15 

October     1 

9.25 

22.6 

2.4 

145.2 

15.7 

1307  A  16 

October    8 

9.72 

78.5 

8.0 

179.5 

18.4 

1307  A  17 

October  15 

9.22 

23.2 

2.5 

156.7 

17.0 

1307  B    1 

June        25 

7.01 

93.5 

13.3 

395.1 

56.3 

1307  B    2 

July           2 

8.90 

4.2 

0.4 

193.6 

21.7 

1307  B    3 

July           9 

11.58 

80.1 

6.9 

207.5 

17.9 

1307  B    4 

July         16 

10.33 

45.3 

4.3 

234.4 

22.6 

1307  B    5 

July         23 

10.42 

45.1 

4.3 

146.7 

14.0 

1307  B    6 

July         30 

11.05 

None 

89.5 

8.1 

1307  B    7 

August      6 

11.33 

34.2 

3'6 

221.6 

19.5 

1307  B    8 

August    13 

10.50 

49.5 

4.7 

273.7 

26.0 

1307  B    9 

August    20 

11.29 

18.8 

1.6 

273.9 

24.2 

1307  B  10 

August    27 

10.04 

47.1 

4.6 

328.9 

32.7 

1307  B  11 

Sept.         3 

9.90 

31.4 

3.1 

418.7 

42.2 

1307  B  12 

Sept.        10 

9.50 

46.0 

4.8 

227.1 

23.9 

1307  B  13 

Sept.        17 

7.20 

21.6 

3.0 

71.4 

9.9 

1307  B  14 

Sept.        24 

8.91 

60.8 

6.8 

117.6 

13.2 

1307  B  15 

October     1 

10.30 

64.8    • 

6.2 

Too  dark 

1307  B  16 

October     8 

8.75 

135.3 

15.4 

124.8  ' 

14'2 

1307  B  17  |  I  October  15 

7.20 

None 

97.1 

13.4 

very  near  the  minimum  necessary  for  complete  precipitation  of  the 
copper.  There  is  little  if  any  excess.  The  amounts  of  copper  in  so- 
lution are  greater  than  from  any  of  the  trees  sprayed  with  standard 
Bordeaux  containing  equal  parts  by  weight  of  copper  sulphate  and 
lime.  It  seems  evident,  therefore,  that  a  certain  excess  of  lime  has  a 
retarding  action  on  the  conversion  of  the  copper  of  Bordeaux  mixture 
into  soluble  forms. 


286 


BULLETIN  No.   135 


[May 


Chemical  Determinations  from  Waters  Collected  from  Trees  1507  A  and  B. 
Exposed  to  atmospheric  conditions 


Soluble  constituents 

Serial 
Number 

Date     . 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1507  A    1 

June        22 

1.93 

67.3 

34.8 

74.6 

38.6 

1507  A    2 

June        24 

37.28 

427.7 

11.4 

289.6 

7.7 

1507  A    3 

July           1 

2.19 

112.7  ' 

51.4 

39.4 

18.0 

1507  A    4 

July           6 

8.81 

368.9 

41.8 

151.7 

17.2 

1507  A    5 

July    9,  10 

23.73 

384.5 

16.2 

37.2 

1.5 

1507  A    6 

July  10,  11 

9.99 

125.2 

12.6 

72.7 

7.2 

1507  A    7 

July  14,  15 

21.51 

24.0 

1.1 

140.5 

6.5 

1507  A    8 

July         17 

6.68 

78.6 

11.7 

102.6 

15.3 

1507  A    9 

July         26 

2.28 

47.0 

20.6 

Too  dark 

1507  A  10 

July         28 

5.70 

66.0 

11.5 

17.7 

3.1 

1507  A  11 

July        31 

15.07 

127.2 

8.4 

28.3 

1.8 

1507  A  12 

August      1 

1.04 

28.7 

22.7 

7.1 

6.8 

1507  A  13 

August      5 

18.72 

62.4 

3.3 

97.8 

5.2 

1507  A  14 

August      7 

16.45 

79.8 

4.8 

98.9 

6.0 

1507  A  15 

August    11 

4.65 

44.4 

9.5 

19.7 

4.2 

1507  A  16  !     August    16 

22.65 

52.3 

2.3 

76.1 

3.3 

1507  A  17 

August    17 

4.39 

•    39.3 

8.9 

40.2 

9.1 

1507  A  18 

August    19 

7.68 

34.7 

4.5 

121.5 

15.8 

1507  A  19 

Sept.   9,  10 

8.03 

65.8 

8.1 

Too  dark 

1507  A  20 

Sept.       27 

7.04 

76.6 

10.8 

Too  dark 

1507  A  21 

October    3 

16.42 

212.0 

12.8 

Too  dark 

1507  A  22 

October     7 

2.30 

18.8 

8.1 

Too  dark 

1507  A  23 

October  15 

2.30 

39.3 

17.0 

Too  dark 

1507  A  24 

October  26 

4.98 

13.7 

2.7 

Too  dark 

1507  B    1 

June        22 

1.83 

177.6 

97.0 

84.1 

45.9 

1507  B    2 

June        24 

37.25 

444.0 

11.9 

317.1 

8.5 

1507  B    3 

July           1 

2.30 

337.3 

146.6 

24.7 

10.7 

1507  B    4 

July           6 

9.32 

452.1 

48.5 

68.0 

7.2 

1507  B    5 

July    9,  10 

24.70 

127  6 

5.1 

475.3 

19.2 

1507  B    6 

July  10,  11 

10.39 

105.0 

10.1 

161.2 

15.5 

1507  B    7 

July  14,  15 

22.89 

174.8 

7.6 

527.3 

23.0 

1507  B    8 

July         17 

7.13 

43.2 

6.0 

304.3 

42.6 

1507  B    9 

July         26 

2.44 

5.6 

2.2 

13.6 

5.5 

1507  B  10 

July         28 

6.47 

24.9 

3.8 

74.0           11.4 

1507  B  11 

July         31 

16.56 

78.9 

4.7 

172.6            10.4 

1507  B  12 

August      1 

1.11 

16.1 

14.5 

60.6 

54.6 

1507  B  13 

August      5 

19.35 

55.0 

2.8 

126.4 

6.5 

1507  B  14 

August      7 

17.15. 

31.4 

1.8 

84.2 

4.9 

1507  B  15 

August    11 

5.10 

55.5 

10.8 

70.6 

13.8 

1507  B  16 

August    16 

28.50 

76.8 

2.6 

66.9 

2.3 

1507  B  17 

August    17 

4.73 

15.5 

3.2 

24.5 

5.1 

1507  B  18 

August    19 

7.50 

16.5 

2.2 

196.2 

26.1 

1507  B  19 

Sept.  9,  10 

8.62 

43.2 

5.0 

Too  dark 

1507  B  20 

Sept.       27 

7.45 

36.6 

4.9 

Too  dark 

1507  B  21 

October     3 

17.34 

106.1 

6.1 

Too  dark 

1507  B  22 

October     7 

2.50 

7.9 

3.1 

Too  dark 

1507  B  23        October  15 

2.32 

7.8 

3.3 

Too  dark 

1507  B  24        October  26 

4.69 

14.7 

3.1 

Too  dark 

1909] 


BORDEAUX  MIXTURE 


287 


Turning  now  to  the  effects  on  foliage  of  this  reduction  in  lime,  it 
may  be  stated  that  the  foliage  of  the  trees  exposed  to  rains  was  very 
seriously  injured.  Brown  spots  appeared  immediately  following  the 
first  rain.  The  injury  continued  to  increase,  and  a  large  part  of  the 
leaves  dropped  off.  Of  leaves  remaining  at  the  close  of  the  season, 
practically  all  were  in  a  damaged  condition. 

•Chemical  Determinations  from  Waters  Collected  from  Trees  1707  A  and  B. 
Protected  from  rain;   sprayed  with  carbonated  water 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1707  A    1 

June        25 

8.97 

228.0 

25.4 

344.6 

38.4 

1707  A    2 

July           2 

5.51 

297.0 

53.9 

38.5 

6.9 

1707  A    3 

July           9 

6.44 

59.7 

9.2 

85.3 

13.2 

1707  A    4 

July         16 

5.67 

233.3 

41.1 

85.8 

15.1 

1707  A    5 

July         23 

6.82 

190.1 

27.8 

83.2 

12.2 

1707  A    6 

July        30 

6.13 

123.7 

20.1 

74.8 

12.2 

1707  A    7 

August      6 

6.60 

92.3 

14.0 

75.9 

11.5 

1707  A    8 

August    13 

6.19 

34.5 

5.5 

30.3 

4.8 

1707  A    9 

August    20 

6.32 

86.3 

13.8 

189.5 

30.0 

1707  A  10 

August    27 

6.19 

131.2 

21.1 

115.6 

18.6 

1707  A  11 

Sept.         3 

7.06 

85.3 

12.0 

147.6 

20.9 

1707  A  12 

Sept.        10 

6.21 

103.6 

16.6 

145.0 

23.3 

1707  A  13 

Sept.        17 

6.26 

110.0 

17.5 

Too  dark 

1707  A  14 

Sept.       24 

6.38 

71.9 

11.2 

86.7 

i^5 

1707  A  15 

October     1 

6.10 

69.1 

11.3 

50.9 

8.3 

1707  A  16 

October     8 

6.30 

42.4 

6.7 

Too  dark 

1707  A  17 

October  15 

6.13 

50.0 

8.1 

32.1 

5^2 

1707  B    1 

June'       25 

4.98 

71.5 

14.3 

58.6 

11.7 

1707  B    2 

July           2 

4.95 

339.5 

68.5 

22.5 

4.5 

1707  B    3 

July           9 

8.25 

113.8 

13.7 

112.2 

13.6 

1707  B    4 

July         16  • 

5.67 

171.7 

30.4 

126.9 

22.3 

1707  B    5 

July        23 

5.61 

137.5 

24.5 

84.7 

15.0 

1707  B    6 

July         30 

6.18 

102.4 

16.5 

65.9 

10.6 

1707  B    7 

August      6 

6.40 

67.4 

10.5 

79.5 

12.4 

1707  B    8 

August    13 

6.56 

67.5 

10.2 

64.3 

9.8 

1707  B    9 

August    20 

7.20 

101.9 

14.1 

210.9 

29.2 

1707  B  10 

August    27 

6.47 

77.8 

12.0 

89.9 

13.8 

1707  B  11 

Sept.         3 

5.86 

69.1 

11.7 

103.3 

17.6 

1707  B  12       Sept.        10 

5.28 

34.9 

6.6 

Too  dark 

1707  B  13       Sept.        17 

5.96 

62.8 

10.5 

Too  dark 

1707  B  14       Sept.       24 

6.38 

66.5 

10.4 

Too  dark 

1707  B  15       October     1 

6.50 

67.1 

10.3 

Too  dark 

1707  B  16       October    8 

7.07 

25.2 

3.5 

76.1 

l6'7 

1707  B  17       October  15 

6.02 

47.1 

7.8 

35.5 

5.8 

The  foliage,  on  the  trees  sprayed  with  carbonated  water,  remained 
perfect  for  a  considerable  time,  but  early  in  September  a  few  of  the 
lower  leaves  became  slightly  spotted.  This  injury  did  not  increase,  and 
the  general  condition  of  foliage  at  the  close  of  the  season  was  rated  as 
excellent.  In  the  matter  of  adhesiveness,  the  four  trees  were  alike. 
They  served  as  an  excellent  illustration  of  the  relation  of  proper  excess 
of  lime  to  adhesiveness.  When  sprayed,  the  trees  were  of  the  normal 


288  BULLETIN  No.   135  [May 

Bordeaux  blue  color.  But,  at  each  washing  with  rain  or  carbonated 
water,  this  color  was  diminished  and  by  the  first  of  September  only 
slight  traces  of  the  mixture  was  diminished  and  by  the  first  of  Sep- 
tember only  slight  traces  of  the  mixture  could  be  found  on  the  leaves. 
On  all  the  trees,  leaves  assumed  the  dark  green  shades  that  have  been 
referred  to  in  connection  with  some  other  trees,  but  the  blue  color 
retained  thruout  the  season  by  leaves  of  trees  sprayed  with  Bordeaux 
having  the  full  complement  of  lime  was  entirely  wanting  or  only  pres- 
ent in  a  few  small  spots. 

Tabulations  of  the  chemical  data  obtained  from  the  waters  from 
the  trees  used  in  this  test  of  carbonated  waters  are  given  on  pages  286 
and  287. 

BORDEAUX  MADE  WITH  AIR-SLAKED  LIME 

The  danger  in  using  air-slaked  lime  has  been  referred  to;  but 
brief  mention  may  here  be  made  of  the  results  obtained  from  two  trees 
treated  with  a  Bordeaux-Paris  green  mixture,  made  after  the  standard 
formula,  but  in  which  air-slaked,  instead  of  fresh-slaked  lime  was 
used.  The  three  applications  were  made  June  19.  Drip  Waters, 
from  the  24  rains  that  fell  between  June  19  and  October  26,  were  col- 
lected, and  examined  for  copper  in  solution.  The  mixture  at  time  of 
application  contained  no  soluble  copper.  Measurable  quantities  of 
copper  in  solution  were  found  in  all  waters  collected,  but  the  amounts 
were  less  than  was  anticipated.  The  maximum  was  70  milligrams  per 
litre,  the  same  as  was  found  for  the  waters  from  the  No.  507  trees. 
The  average  copper  in  solution  was  8.9  milligrams  per  litre  for  the  two 
trees  here  considered,  while  for  the  No.  507  -trees  it  was  9.2  milli- 
grams per  litre.  This  is  a  fairly  close  approximation  for  these  two 
pairs  of  trees  in  this  matter  of  copper  in  solution.  The  striking  differ- 
ences between  the  two  pairs  of  trees  were : 

1.  In  amount  of  injury  to  foliage.     The  injury  appearing  on 
leaves  of  the  No.  507  trees  has  been  described  as  slight,  and  as  first 
appearing  62  days  after  application  of  the  spray.     The  injury  to  foli- 
age of  the  two  trees  treated  with  Bordeaux  made  with  air-slaked  lime 
was  very  serious,  resulting  in  the  early  loss  of  a  large  portion  of  the 
leaves.     Brown  spots  appeared  in  considerable  numbers  immediately 
following  the  first  rain  June  22,  and  the  injury  continued  to  increase 
for  several  weeks.     Many  leaves  became  wholly  brown  and  promptly 
dropped  off.     It  is  recorded  in  the  notes  made  September  4 — that  fully 
half  the  leaves  had  then  fallen  and  those  remaining  were,  almost  with- 
out exception,  more  or  less  injured  by  brown  spots. 

2.  In  regard  to  adhesiveness.     Bordeaux  applied  to  the  No.  507 
trees  was  as  adhesive  as  possible ;  spots  or  splashes  having  the  normal 
Bordeaux  blue  color  remained  on  practically  all  leaves,  and  many  were 
still  completely  coated  at  the  close  of  the  season. 

On  the  other  pair  the  air-slaked  lime  Bordeaux  did  not  give  to  the 
leaves  a  normal  color  when  applied.  It  lacked  the  bright  blue  character- 
istic of  well  made  mixtures  and  appeared  dull  and  dingy.  Each  rain 
reduced  the  color  perceptibly  and  by  the  first  of  August  there  remained 
only  a  few  small  spots  on  some  of  the  leaves.  In  fact  casual  examin- 


1909] 


BORDEAUX  MIXTURE 


289 


Chemical  Determinations  from  Waters  Collected  from  Trees  1407  A  and  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 
drip 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1407  A    1 

June        22 

2.01 

140.4 

69.8 

78.3 

38.9 

1407  A    2 

June        24 

39.15 

194.2 

4.9 

467.7 

11.9 

1407  A    3 

July           1 

2.47 

34.4 

13.9 

45.7 

18.5 

1407  A    4 

July           6 

8.49 

58.8 

6.9 

193.5 

22.7 

1407  A    5 

July           9 

25.34 

189.2 

7.4 

145.7 

5.7 

1407  A    6 

July  10,  11 

10.07 

110.0 

10.8 

123.7 

12.2 

1407  A    7 

July  14,  15 

23.39 

90.0 

3.8 

410.0 

17.5 

1407  A    8 

July         17 

6.83 

68.3 

10.0 

72.7 

10.6 

1407  A    9 

July         26 

2.61 

11.7 

4.4 

31.7 

12.1 

1407  A  10 

July        28 

6.85 

110.5 

16.1 

19.6 

2.8 

1407  A  11 

July        31 

17.13 

106.1 

6.1 

80.1 

4.6 

1407  A  12 

August      1 

1.10 

43.2 

39.2 

7.4 

6.7 

1407  A  13 

August      5 

20.63 

152.7 

7.4 

112.5 

5.4 

1407  A  14 

August      7 

17.29 

116.6 

6.7 

81.1 

4:6 

1407  A  15 

August    11 

5.16 

56.1 

10.8 

39.7 

7.6 

1407  A  16 

August    16 

29.07 

89.4 

3.0 

175.8 

6.0 

1407  A  17 

August    17 

4.81 

18.9 

3.9 

41.3 

8.5 

1407  A  18 

August    19 

8.13 

60.0 

7.3 

103.1 

12.6 

1407  A  19 

Sept.   9,  10 

8.26 

47.1 

5.7 

Too  dark 

1407  A  20 

Sept.       27 

7.64 

Lost 

Lost 

Too  dark 

1407  A  21 

October     3 

17.78 

49.1 

2.8 

Too  dark 

1407  A  22 

October     7 

2.55 

15.7 

6.1 

Too  dark 

1407  A  23 

October  15 

2.50 

11.0 

4.4 

Too  dark 

1 

1407  A  24 

October  26 

4.93 

39.4 

7.9 

Too  dark 

1407  B    1 

June        22 

2.17 

54.2 

24.9 

98.7 

45.4 

1407  B    2 

June        24 

41.04 

127.3 

3.1 

461.7 

11.2 

1407  B    3 

July           1 

2.27 

3.9 

1.7 

32.9 

14.4 

1407  B    4 

July           6 

9.01 

46.8 

5.0 

223.5 

24.8 

1407  B    5 

July           9 

25.64 

154.0 

6.0 

147.5 

5.7 

1407  B    6 

July  10,  11 

10.81 

77.7 

7.1 

294.9 

27.2 

1407  B    7 

July  14,  15 

23.04 

31.4 

1.3 

150.5 

6.5 

1407  B    8 

July         17 

6.92 

47.4 

6.8 

82.9 

11.9 

1407  B    9 

July         26 

2.86 

26.7 

9.3 

70.6 

24.6 

1407  B  10 

July         28 

6.94 

59.0 

8.5 

14.5 

2.0 

1407  B  11 

July        31 

17.28 

106.1 

6.1 

49.4 

2.8 

1407  B  12 

August      1 

1.19 

28.7 

24.1 

15.7 

13.1 

1407  B  13 

August      5 

20.60 

72.3 

3.5 

137.4 

6.6 

1407  B  14 

August      7 

17.33 

60.0 

3.4 

141.2 

8.1 

1407  B  15 

August    1  1 

5.32 

57.0 

10.7 

113.5 

21.3 

1407  B  16 

August    16 

29.20 

51.6 

1.7 

259.6 

8.8 

1407  B  17 

August    17 

5.00 

3.4 

0.6 

78.5 

15.7 

1407  B  18 

August    19 

7.95 

16.0 

2.0 

49.7 

6.2 

1407  B  19 

Sept.   9,  10 

9.62 

49.5 

5.1 

Too  dark 

1407  B  20 

Sept.       27 

7.81 

47.1 

6.0 

Too  dark 

1407  B  21 

October     3 

17.88 

18.8 

1.0 

Too  dark 

1407  B  22 

October     7 

2.75 

15.5 

5.6 

Too  dark 

1407  B  23 

October  15 

2.55 

9.4 

3.6 

7.8 

3'6 

1407  B  24 

October  26 

5.28 

13.4 

2.5 

Too  dark 

290  BULLETIN  No.   135  [May 

ation  at  this  time  gave  the  impression  that  the  trees  had  not  been 
sprayed. 

Soluble  copper,  however,  continued  to  appear  in  the  waters  col- 
lected, and  in  amounts  averaging  about  20  percent  above  the  average 
for  all  waters.  It  appears  that  all  surplus  lime  and  all  calcium  sul- 
phate were  quickly  washed  away,  leaving  a  considerable  amount  of 
copper  upon  the  trees.  That  this  copper  was  in  some  slowly  soluble 
form  is  shown  by  the  small  amounts  given  up  to  the  waters  passing 
over  the  trees ;  that  it  possessed  considerable  adhesiveness  is  apparent 
from  its  regular  appearance  during  more  than  2l/2  months  from  the 
time  of  practical  disappearance  of  the  blue  color ;  that  it  possessed  the 
power  to  act  injuriously  upon  leaves,  the  continued  loss  of  foliage 
thru  burning  fully  testified.  The  chemical  data  necessary  to  the  satis- 
factory solution  of  several  questions  that  are  suggested  by  the  behavior 
of  the  mixture  applied  to  these  trees  are  not  at  hand,  and  these  ques- 
tions must  be  added  to  the  already  long  list  of  matters  demanding  fur- 
ther investigation. 

It  is  a  further  fact  regarding  these  trees,  that  uninjured  portions 
of  leaves  assumed  a  very  dark  green  color,  as  was  determined  by 
comparison  with  leaves  from  other  sprayed  trees  and  from  trees  that 
had  not  been  sprayed.  Determinations  of  copper  in  solution  in  waters 
collected  from  the  trees  sprayed  with  air-slaked  lime,  are  given  in  tab- 
ular form  page  289. 

SOLUBILITY  OF  COPPER  UNDER  THE  INFLUENCE  OF  LONG  CONTINUED 
MOIST  CONDITIONS  AND  UNDER  SPRAY  APPLIED  AT  FREQUENT 

INTERVALS 

Certain  irregularities  in  the  amounts  of  copper  found  in  solution 
in  the  waters,  collected  from  trees  in  1906,  brought  up  the  question — • 
Does  the  copper  become  soluble  gradually  and  accumulate  as  soluble 
copper  on  the  leaves  during  intervals  between  rains  or  sprays,  or  is  it 
made  soluble  under  the  direct  action  of  the  water  passing  over  the 
leaves  ? 

To  obtain  information  on  this  matter,  two  trees  were  prepared 
with  covers  to  protect  from  rain,  and  with  the  arrangements  for  col- 
lecting waters  sprayed  over  the  leaves.  Both  trees  were  given  three 
heavy  applications  of  standard  Bordeaux-Paris  green  mixture  on 
June  17.  It  was  proposed  that  after  an  interval  of  a  few  days,  one 
tree  should  be  sprayed,  allowed  to  dry,  then  sprayed  again  and  this 
repeated  as  many  times  as  possible  during  the  day.  The  other  tree  to 
be  kept  continuously  wet  during  a  day,  with  a  final  spray  at  night. 
These  treatments  were  to  be  repeated  at  intervals  thru  the  season.  Be- 
cause of  the  large  amount  of  work  demanded  by  the  numerous  experi- 
ments in  progress  it  was  found  impossible  to  carry  out  the  original 
plan.  Only  two  all-day  treatments  were  given,  the  first  July  22,  thirty- 
five  days  after  the  trees  had  received  the  coating  of  Bordeaux,  and  the 
second  August  28,  after  an  interval  of  37  days.  At  8:00  a.  m.  July 
22,  one  tree  was  sprayed  with  about  seven  litres  of  cistern  water,  the 
jar  emptied  and  the  tree  allowed  to  dry.  It  was  found  that  one  hour 


1909] 


BORDEAUX  MIXTURE 


291 


served  to  fully  dry  the  foliage.  A  second  application  was  made  at 
9:00  a.  m.  and  others  followed  at  one  hour  intervals.  Ten  lots  of 
water  were  taken  during  the  day.  Commencing  at  the  same  time  in 
the  morning  the  other  tree  was  sprayed  with  just  enough  water  to 
moisten  the  leaves,  and  additional  applications  were  made  with  such 
frequency  that  a  continually  wet  condition  of  the  leaves  was  maintained 
thruout  the  day.  As  little  water  as  possible  was  used,  but  small  quan- 
tities continually  dripped  into  the  jar  and  at  evening  the  amount  col- 
lected amounted  to  nearly  nine  litres.  This  water  was  removed  and 
then  the  tree  was  sprayed  with  about  7  litres,  which  was  also  con- 
Chemical  Determinations  from  Waters  Collected  from  Trees  1107  A  and  1107  B. 


Soluble  constituents 

Serial 
Number 

Date 

Amount 
of 

Copper 

Alkalinity  in  terms 
of  calcium  oxide 

Total 

Per  litre 

Total 

Per  litre 

1107  A    1 

July         22 

6.93 

6.2 

0.8 

194.9 

28.1 

1107  A    2 

July        22 

7.39 

15.3 

2.0 

127.7 

17.2 

1107  A    3 

July        22 

6.68             23.9 

3.5 

113.0 

16.9 

1107  A    4 

July       22           6.95             10.5 

1.5 

110.7 

15.9 

1107  A    5 

July         22 

6.69 

18.6 

2.7 

96.1 

14.3 

1107  A    6 

July         22 

6.85 

1.7 

0.2 

78.8 

11.5 

1107  A    7 

July         22 

6.55               5.3 

0.8 

80.3 

12.2 

1107  A    8 

July         22 

7.66 

18.8 

2.4 

84.0 

10.9 

1107  A    9 

July        22 

5.90 

None 

103.4 

17.5 

1107  A  10 

July        22 

7.82 

None 

150.9 

19.2 

1107  A  11 

August    28 

7.56 

64.8 

8.5 

230.5 

30.4 

1107  A  12 

August    28 

7.85 

14.1 

1.8 

208.8 

26.5 

1107  A  13 

August    28 

6.96 

14.7 

2.1 

109.1 

15.6 

1107  A  14 

August    28 

8.56 

31.1 

3.6 

145.2 

16.9 

1107  A  15 

August    28 

9.39 

21.7 

2.3 

161.4 

17.1 

1107  A  16 

August    28 

11.00 

None 

149.6 

13.6 

1107  A  17 

August    28 

6.45 

13.8 

2.1 

106.2 

16.4 

1107  A  18 

August    28 

9.70 

11.3 

1.1 

272.1 

28.0 

1107  A  19 

August    28 

8.37 

18.8 

2.2 

141.8 

16.9 

1107  B    1 

July         22 

8.81             23.1 

2.6 

204.8           23.2 

1107  B    2 

July         22           6.96             Lost 

211.7           30.5 

1107  B    3 

August    28 

12.70 

70.7 

5.5 

385.8 

30.3 

1107  B    4 

August    28 

8.75 

None 

145.0 

16.5 

lected  and  reserved  for  analysis.  August  28,  the  same  procedure  was 
repeated,  except  that  only  9  waters  were  collected  from  the  tree 
sprayed  at  1  hour  intervals. 

The  average  of  all  lots  of  water,  collected  from  the  trees,  sprayed 
at  one  hour  intervals,  was  7.68  litres.  Copper  was  found  in  solution 
in  lots  1  to  8  July  22.  Lots  9  and  10  contained  none.  Of  the  waters 
August  28 — all  except  the  sixth  contained  copper  in  solution.  The 
amounts  were  small  in  all  waters.  The  maximumi  of  July  22  was  3.5 
milligrams  per  litre  in  the  third  lot.  August  28  the  maximum  8.5 
milligrams  per  litre  appeared  in  the  first  water.  Succeeding  amounts 
ranged  between  1.1  milligrams  per  litre  in  the  eighth  and  3.6  milligrams 


292  BULLETIN  No.   135  [May 

per  litre  in  the  fourth.  Lot  No.  9  the  last,  contained  2.2  milligrams  per 
litre.  The  average  was  1.77  milligrams  per  litre  on  the  earlier  date 
and  2.97  milligrams  on  August  28. 

The  small  amount  of  copper  in  solution  (0.8  milligrams  per  litre) 
in  the  first  water  of  July  22,  indicates  that  no  process  of  conversion  of 
copper  to  soluble  forms  could  have  been  in 'operation  during  the  35 
days  from  application  of  the  Bordeaux  to  first  spraying  with  water. 
That  some  conversion  took  place  in  the  interval  between  July  22  and 
August  28  is  indicated  by  the  fact  that  more  than  one  third  of  the 
total  copper  found  in  the  nine  waters  was  recovered  from  the  first  lot 
of  water  collected.  Subsequent  waters,  except  the  sixth,  contained 
small  amounts  but  enough  to  show  that  the  solvent  action  takes  place 
under  direct  applications.  The  uniformly  small  amounts  of  copper, 
appearing  in  solution,  attest  the  slow  solubility  of  the  Bordeaux,  under 
the  conditions  imposed  in  this  test. 

The  water  from  the  tree,  kept  continually  moist  July  22,  yielded 
2.6  milligrams  of  soluble  copper  per  litre.  The  water  from  the  after 
spray  was  lost  through  accident.  On  the  later  date,  the  drip  accumu- 
lated during  the  day  gave  5.5  milligrams  per  litre,  and  the  lot  of  water 
from  the  after  spray  contained  no  copper.  Apparently  a  long  contin- 
ued moist  condition  of  foliage  maintained  by  water  applied  as  a  spray 
does  not  increase  the  solubility  of  the  copper  in  Bordeaux  to  any  ap- 
preciable extent.  The  foliage  of  the  two  trees  remained  in  perfect 
condition  during  the  test.  Determinations  of  soluble  copper  and  lime 
are  given  in  tabular  form  page  291. 

CONCLUSIONS 

The  observations  and  experiments  recorded  in  the  foregoing  pages 
are  presented  as  a  report  of  progress  of  an  investigation  of  Bordeaux 
mixture  in  its  relations  to  orchard  trees  and  particularly  with  refer- 
ence to  its  effects  upon  foliage. 

The  primary  problem  is  complex,  presenting  several  distinct 
phases.  Each  of  these  phases  when  subjected  to  definite  experiments 
broadened  and  subdivided  until  the  field  of  the  investigation  extended 
beyond  anticipated  limits.  Some  of  the  lines  of  experiments  have 
given  results  from  which  fairly  definite  conclusions  were  possible. 
Other  lines  of  experiments  have  been  characterized  by  anomalous  or 
directly  contradictory  results  that  have  proved  perplexing,  difficult  to 
interpret  and  that  demanded  repetition  or  extension  of  the  experiments 
instead  of  leading  to  definite  conclusions*  Such  results  have  occurred 
rather  frequently  and  are  ascribed,  in  great  part,  to  the  intimate  rela- 
tions between  variable  and  interdependent  factors  that  are  difficult  to 
isolate ;  such  as  the  phenomena  included  under  the  term  atmospheric 
conditions. 

Where  conflict  and  obscurity  attend  the  results  of  experiments,  it 
is  only  by  repetition  and  continued  observation  of  accompanying  cir- 
cumstances that  reasons  for  conflicts  can  be  determined  and  the  uncer- 
tainties that  stand  in  the  way  of  definite  conclusions  cleared  away. 


1909]  BORDEAUX  MIXTURE  293 

This  procedure  requires  time  and  sufficiently  explains  why  the  investi- 
gation has  been  prolonged  and  why  it  must  be  continued  in  order 
to  reach  satisfactory  conclusions  on  the  many  points  involved. 

Owing  to  'the  exacting  nature  of  the  details  attending  the  some- 
what extended  experiments  relating  to  soluble  copper  in  waters  from 
sprayed  trees,  other  phases  of  the  problem  have  been  held  in  abey- 
ance or  have  received  but  little  attention.  Investigation  of  these  phases 
will  be  pushed  during  the  present  season  and  it  is  hoped  that  definite 
conclusions  may  be  reached  regarding  some  of  the  important  questions 
involved. 

The  subjects  discussed  in  the  present  paper  may  be  epitomized 
as  follows: 

1.  Injury  to  foliage  of  apple  trees  following  applications  of  Bor- 
deaux mixture  is  of  common  occurrence.  Much  of  the  injury  reported 
or  observed  is  preventable.     The  principal  sources  of  injury  as  deter- 
mined by  observation  are — 

1.  Use  of  impure  or  improper  materials. 

2.  Carelessness  in  making  the  mixtures. 

3.  Improper  and  ineffective  application. 

The  first  two  of  these  sources  of  difficulty  can  be  entirely  elim- 
inated and  the  third  greatly  mitigated  by  reasonable  attention  and  su- 
pervision. Formulas  must  be  respected  and  small  details  of  practice 
must  receive  attention  in  order  to  attain  best  results. 

But  when  all  precautions  have  been  taken  injury  sometimes  re- 
sults. These  non-preventable  injuries  are  associated  with  unfortunate 
weather  conditions  and  particularly  with  the  action  of  rain  and  dew. 

2.  The  chemical  changes  occurring  in  making  Bordeaux  mixture 
are  still  involved  in  some  obscurity.     That  the  copper  is  deposited  in 
the  form  of  copper  hydroxide,  as  has  been  generally  accepted,  is  denied 
by  Professor  Pickering  who  also  points  out  the  difficulty  attending 
analysis  of  the  precipitate  formed. 

3.  The  adhesiveness  of  Bordeaux  mixture  depends  very  much 
upon  the  manner  of  making  and  upon  the  character  of  the  lime  used. 
Variation  in  the  proportions  of  copper  sulphate  and  lime  beyond  cer- 
tain well-defined  limits  decreases  adhesiveness.     With  lime  of  good 
quality  a  close  approximation  of  equal  parts,  of  copper  sulphate  and 
lime  gives  greatest  adhesiveness. 

There  is  decided  advantage  in  the  maintenance  of  an  excess  of 
lime  upon  the  foliage,  but  this  must  be  accomplished  by  subsequent 
applications  and  not  by  increasing  the  amount  in  the  original  mixture. 

4.  No  deunite  experiments  regarding  the  accumulation  of  copper 
in  the  soil  under  sprayed  trees  have  been  conducted,  but  from  results 
reported  of  experiments  of  others  it  does  not  appear  that  there  is 
danger  from  this  source.     There  is  no  evidence  at  hand  that  in  any 
way  associates  browning  or  yellowing  of  foliage  with  copper  in  the 
soil. 

5.  The  two  classes  of  leaf  injury  considered  are,  "Brown-spot- 
ting" and  "Yellowing."     Brown-spotting  is  the  more  common  injury. 


294  BULLETIN  No.  135  [May 

Yellowing,  when  it  appears  in  epidemic  form,  is  the  more  serious 
of  the  two  because  affected  leaves  are  entirely  destroyed. 

Not  all  brown-spotting  is  due  to  spraying.  Other  causes  are, 
frosts,  winds  accompanying  cold  spring  storms,  fungi  and  insects. 

Leaf  injuries  are  most  common  and  most  serious  in  neglected 
orchards.  Much  of  the  injury  following  spraying  is  attributable  to 
abrasions  of  the  epidermis  made  by  insects,  and  to  infection  by  fungi 
preceding  spraying. 

6.  The  ideal  spray  compound  that  is  perfectly  effective  and  at 
the  same  time  perfectly  harmless  on  all  occasions  and  under  all  con- 
ditions has  not  yet  been  discovered.     Bordeaux  mixture  most  nearly 
approximates  the  ideal,  but  its  harmlessness  can  not  be  absolutely  de- 
pended upon. 

7.  Injuries  to  foliage  do  sometimes  follow  applications  of  Bor- 
deaux mixture  and  appear  to  be  unavoidable.     There  are  differences 
of  opinion  as  to  the  exact  manner  in  which  injuries  are  inflicted.     The 
important  questions  involved  are :    1 — The  agencies  thru  which  copper 
deposited  on  the  leaves  become  soluble,  and  2 — The  manner  in  which 
the  toxic  action  is  communicated  to  the  cell  protoplasm.     The  carbon 
dioxide  contained  in  the  air  and  in  meteoric  waters  is  accepted  as  an 
active  agent  in  rendering  soluble  the  copper  of  Bordeaux  mixture  and 
it  is  believed  that  the  ammonium  compounds  brought  down  by  rain 
may  also  exert  a  solvent  action  on  the  copper. 

8.  Laboratory  experiments  gave  results  showing  that  the  copper 
of   Bordeaux  mixture  remained   insoluble   for   long  periods.     These 
results  accord  with  the  results  of  similar  laboratory  experiments  re- 
ported by  Millardet  and  Gayon  and  on  which  they  based  their  claim 
that  the  copper  of  Bordeaux  mixture,  as  deposited  on  leaves,  remains 
insoluble  as  long  as  free  lime  is  present. 

Field  experiments,  however,  directly  contradict  the  laboratory 
results  and  show  conclusively  that,  under  orchard  conditions,  copper, 
in  small  quantity,  becomes  soluble  very  soon  after  deposition  and  con- 
tinues to  appear  as  long  as  any  of  the  mixture  remains  upon  the  leaves. 
The  presence  of  lime  in  excess  does  not  prevent  solution  of  the  copper. 

9.  No  evidence  has  been  obtained  in  support  of  the  suggestions 
of  authors  that  solution  of  copper  occurs  thru  the  agency  of  germin- 
ating spores,  or  thru  secretions  from  leaf  surfaces. 

10.  Actual  demonstration  of  the  presence  of  copper  in  dead  leaf 
cells  has  not  been  made,  but  the  theory  of  penetration  and  of  death  of 
cell  protoplasm  by  direct  contact  with  copper  is  regarded  as  more  prob- 
able than  the  theory  of  transmission  of  toxic  effect  without  penetra- 
tion as  advanced  by  Rumm. 

11.  The  value  of  Bordeaux  mixture  as  a  fungicide  depends  upon 
the  contained  copper.     The  action  is  preventive  and  not  curative.     It 
follows  that  early  application  with  the  one  aim  of  defense  gives  infi- 
nitely better  results  than  later  application  intended  to  check  ravages 
already  begun. 

12.  Spores  of  different  fungi  resist  the  action  of  copper  in  vary- 
ing degrees.     Millardet  and   Gayon   found  that  solutions   of  copper 


1909]  BORDEAUX  MIXTURE  295 

sulphate  2  or  3 : 10,000,000  would  prevent  infection  by  zoospores  of 
grape  mildew.  Our  tests  with  spores  of  the  apple  scab  fungus  show 
that  solutions  of  copper  sulphate  1 : 100,000  slightly  retard  germination 
and  that  the  concentration  necessary  to  entirely  prevent  germination 
lies  between  1 :25,000  and  1 : 10,000. 

In  the  stronger  solution  some  of  the  common  moulds  grew  with 
apparently  undiminished  vigor. 

13.  The  causes  of  yellowing  of  leaves  of  apple  trees  are  ob- 
scure and  not  well  understood.     From  observations  extending  over 
five  seasons  it  seems  certain  that  there  are  several  causes  which  may 
operate  singly,  or  together.     Recurrent  epidemics  of  yellowing  appear 
to.  have  no  direct-  relation  to  wet  or  dry  periods,  or  to  other  weather 
conditions.     The  experiments  made  do  not  establish  any  direct  and 
positive  connection  between  spraying  with  well-made  Bordeaux  mix- 
ture and  yellowing  of  leaves,  but  do  show  that  improperly  made  mix- 
tures may  cause  yellowing  and  that  yellowing  results  from  use  of  sim- 
ple solutions  of  copper  sulphate. 

14.  Healthy  bark  of  apple  trees  is  impermeable  to  Bordeaux  mix- 
ture and  solutions  of  copper  sulphate.     Copper  sulphate  solutions  are 
absorbed  thru  wounds  and  promptly  kill  the  leaves  which  then  become 
brown.     Numerous  experiments  in  which  copper  sulphate  solutions 
varying  from  1 :100  to  1 : 1,000  were  injected  thru  roots  and  thru  holes 
bored  in  trunks  of  trees,  uniformly  resulted  in  browning  of  leaves. 
The  copper  penetrates  to  the  leaves  as  was  determined  by  analysis. 
The  time  required  to  give  evidence  of  injury  varies  with  the  strength 
of  the  solution  and  the  rate  of  transpiration,  but  is  usually  short,  vary- 
ing from  25  minutes  in  one  case  to  several  hours  where  the  weaker 
solutions  were  used.     A  further  series  of  experiments  in  which  much 
less  concentrated  solutions  were  used  was  commenced  rather  late  in 
the  season  and  is  to  be  repeated  this  year.     One  tree  in  this  series  sup- 
plied with  a  solution  of  copper  sulphate  1 :25,000  developed  unmistak- 
able yellowing  of  leaves  on  branches  situated  in  the  direct  track  of  the 
ascending  solution. 

15.  The  importance  of  rain  and  dew  as  agents  causing  brown- 
spotting  of  foliage  following  applications  of  Bordeaux  mixture  is  well 
attested  by  the  uniform  results  obtained  from  the  experiments  with 
covered  and  uncovered  trees.     Two  trees  were  sprayed  heavily;  one 
was  left  exposed,  the  other  was  protected  from  all  rain  and  dew.     This 
was  repeated  during  three  seasons.     In  each  year  the  foliage  of  the 
exposed  tree  was  more  or  less  injured  by  brown  spots,  while  the  tree 
protected  from  rain  remained  free  from  injury. 

Several  other  experiments  in  which  trees  exposed  to  rain  were 
brought  into  contrast  with  trees  protected  from  rain  gave,  in  all  cases, 
the  same  results,  namely,  some  degree  of  injury  to  foliage  exposed  to 
rain  and  absolute  freedom  from  injury  to  the  foliage  of  trees  pro- 
tected from  rain. 

16.  Milk  of  lime  does  not  cause  brown  spots  even  when  applied 
in  large  quantity,  but  burning  quickly  follows  applications  of  copper 


296  BULLETIN  No.   135  [May 

sulphate  solutions  even  when  the  solutions  are  very  dilute.  It  is  there- 
fore concluded  that  copper  in  solution  is  the  active  agent  responsible 
for  the  burning  of  foliage. 

17.  From  comparisons  between  leaves  sprayed  with  Bordeaux 
mixture  and  milk  of  lime,  with  Bordeaux  mixture  only,  with  milk  of 
lime  only,  and  leaves  that  had  not  been  sprayed  it  was  found  that  all 
leaves  on  which  lime  had  been  used  were  distinctly  larger  than  those 
receiving  no  milk  of  lime.     This  suggests  a  stimulating  action  on  the 
part  of  the  lime,  whether  by  direct  action  on  the  leaves,  or  by  reason 
of  the  protective  covering  afforded  has  not  been  determined. 

18.  Bordeaux  mixture  has  a  decided  influence  upon  the  color  of 
leaves.     Under  a  coating  of  Bordeaux  mixture  leaves  assume  a  very 
dark  green  color  that  is  retained  even  after  the  coating  is  mostly 
washed  away.     Leaves  coated  with  lime  only  become  in  some  degree 
darker  in  color  than  untreated  leaves,  but  the  shade  is  not  so  deep  as 
is  assumed  under  a  coating  of  Bordeaux  mixture. 

19.  The    frequently   expressed   opinions   that   character   of   the 
storm  influences  the  rate  of  solution  and  the  amount  of  soluble  copper 
on  leaves,  and  the  suggestion  that  electrical  storms  tend  to  increase  the 
amount  of  copper  in  solution  and  the  subsequent  injury  to  foliage  gain 
no  support  from  the  results  of  our  experiments.     There  appears  to  be 
no  correlation  between  the  character  of  the  storm  and  the  rate  of  solu- 
bility or  the  amount  of  copper  found  in  solution  in  the  waters  col- 
lected from  sprayed  trees.     Neither  is  there  any  evidence  that  electrical 
storms  increase  the  amounts  of  copper  in  solution. 

ACKNOWLEDGMENTS 

From,  the  beginning  of  this  investigation  of  Bordeaux  mixture  it 
was  understood  that  the  problems  to  be  solved  were  largely  chemical 
rather  than  horticultural  and  that  the  cooperation  of  a  chemist  would 
be  necessary.  In  July  1906  the  services  of  Mr.  O.  S.  Watkins  were 
secured  and  he  began  work,  under  the  direction  of  Dr.  H.  S.  Grindley, 
in  one  of  the  laboratories  of  the  department  of  chemistry  of  the 
University.  As  the  work  progressed  and  extensions  were  decided 
upon,  a  laboratory  within  the  department  of  horticulture  and  especially 
equipped  for  the  work  was  deemed  essential  to  rapid  and  satisfactory 
conduct  of  the  investigation.  In  the  spring  of  1907  such  a  laboratory 
was  provided.  Since  the  installation  of  necessary  apparatus  all  deter- 
minations of  copper  have  been  made  by  an  electrolytic  process. 

All  determinations  tabulated  in  connection  with  experiments  given 
in  detail  in  preceding  pages  were  made  by  Mr.  Watkins  who  has  been 
in  charge  of  the  laboratory  and  who  has  also  rendered  efficient  aid  in 
the  conduct  of  field  work.  The  writer  is  also  under  many  obligations 
to  Dr.  H.  S.  Grindley  for  frequent  counsel  and  advice  in  matters 
touching  the  chemical  phases  of  the  problems  undertaken. 


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